Graptolites are a group of
colonial animals, members of the subclass Graptolithina within the
class
Class or The Class may refer to:
Common uses not otherwise categorized
* Class (biology), a taxonomic rank
* Class (knowledge representation), a collection of individuals or objects
* Class (philosophy), an analytical concept used differentl ...
Pterobranchia
Pterobranchia is a class of small worm-shaped animals. They belong to the Hemichordata, and live in secreted tubes on the ocean floor. Pterobranchia feed by filtering plankton out of the water with the help of cilia attached to tentacles. The ...
. These
filter-feeding
Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feedin ...
organisms are known chiefly from
fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
s found from the
Middle Cambrian
Middle or The Middle may refer to:
* Centre (geometry), the point equally distant from the outer limits.
Places
* Middle (sheading), a subdivision of the Isle of Man
* Middle Bay (disambiguation)
* Middle Brook (disambiguation)
* Middle Creek (di ...
(
Miaolingian
The Miaolingian is the third Series of the Cambrian Period, and was formally named in 2018. It lasted from about to million years ago and is divided in ascending order into 3 stages: the Wuliuan, Drumian, and Guzhangian. The Miaolingian is prec ...
,
Wuliuan
The Wuliuan stage is the fifth stage of the Cambrian, and the first stage of the Miaolingian Series of the Cambrian. It was formally defined by the ICS in 2018.
Its base is defined by the first appearance of the trilobite species ''Oryctocephalu ...
) through the
Lower Carboniferous
Lower may refer to:
*Lower (surname)
*Lower Township, New Jersey
*Lower Receiver (firearms)
*Lower Wick
Lower Wick is a small hamlet located in the county of Gloucestershire, England. It is situated about five miles south west of Dursley, eight ...
(
Mississippian).
A possible early graptolite, ''
Chaunograptus
''Chaunograptus'' is a genus of putative graptolite known from the Middle Cambrian Burgess Shale. 11 specimens of ''Chaunograptus'' are known from the Greater Phyllopod bed
The Phyllopod bed, designated by USNM locality number 35k, is the most ...
'', is known from the Middle Cambrian.
Recent analyses have favored the idea that the living pterobranch ''
Rhabdopleura
''Rhabdopleura'' is a genus of colonial sessile hemichordates belonging to the Pterobranchia class. As one of the oldest living genera with a fossil record dating back to the Middle Cambrian, it is also considered to be the only living genus of ...
'' represents an extant graptolite which diverged from the rest of the group in the Cambrian.
Fossil graptolites and ''Rhabdopleura'' share a colony structure of interconnected zooids housed in organic tubes (theca) which have a basic structure of stacked half-rings (fuselli). Most extinct graptolites belong to two major orders: the bush-like
sessile
Sessility, or sessile, may refer to:
* Sessility (motility), organisms which are not able to move about
* Sessility (botany), flowers or leaves that grow directly from the stem or peduncle of a plant
* Sessility (medicine), tumors and polyps that ...
Dendroidea
Graptolites are a group of Colony (biology)#Modular organisms, colonial animals, members of the subclass Graptolithina within the class (biology), class Pterobranchia. These Filter feeder, filter-feeding organisms are known chiefly from fossils ...
and the
planktonic
Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...
, free-floating
Graptoloidea
Graptolites are a group of colonial animals, members of the subclass Graptolithina within the class Pterobranchia. These filter-feeding organisms are known chiefly from fossils found from the Middle Cambrian (Miaolingian, Wuliuan) through the L ...
. These orders most likely evolved from encrusting pterobranchs similar to ''Rhabdopleura''. Due to their widespread abundance, plantkonic lifestyle, and well-traced evolutionary trends, graptoloids in particular are useful
index fossils
Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them.Hine, Robert. “Biostratigraphy.” ''Oxford Reference: Dictionary of Bi ...
for the
Ordovician
The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start ...
and
Silurian
The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...
periods.
The name graptolite comes from the
Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group.
*Greek language, a branch of the Indo-European language family.
**Proto-Greek language, the assumed last common ancestor ...
''graptos'' meaning "written", and ''lithos'' meaning "rock", as many graptolite fossils resemble
hieroglyphs
A hieroglyph (Greek for "sacred carvings") was a character of the ancient Egyptian writing system. Logographic scripts that are pictographic in form in a way reminiscent of ancient Egyptian are also sometimes called "hieroglyphs". In Neoplatonis ...
written on the rock.
Linnaeus
Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the ...
originally regarded them as 'pictures resembling fossils' rather than true fossils, though later workers supposed them to be related to the
hydrozoans
Hydrozoa (hydrozoans; ) are a taxonomic class of individually very small, predatory animals, some solitary and some colonial, most of which inhabit saline water. The colonies of the colonial species can be large, and in some cases the specialized ...
; now they are widely recognized as
hemichordates
Hemichordata is a phylum which consists of triploblastic, enterocoelomate, and bilaterally symmetrical marine deuterostome animals, generally considered the sister group of the echinoderms. They appear in the Lower or Middle Cambrian and include ...
.
History
The name "graptolite" originates from the genus ''Graptolithus'' ("writing on the rocks"), which was used by
Linnaeus
Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the ...
in 1735 for inorganic
mineralizations and incrustations which resembled actual fossils. In 1768, in the 12th volume of ''
Systema Naturae
' (originally in Latin written ' with the ligature æ) is one of the major works of the Swedish botanist, zoologist and physician Carl Linnaeus (1707–1778) and introduced the Linnaean taxonomy. Although the system, now known as binomial nomen ...
'', he included ''G. sagittarius'' and ''G. scalaris'', respectively a possible plant fossil and a possible graptolite. In his 1751 ''Skånska Resa'', he included a figure of a "fossil or graptolite of a strange kind" currently thought to be a type of ''
Climacograptus
''Climacograptus'' is an Ordovician to Silurian genus of graptolite
Graptolites are a group of colonial animals, members of the subclass Graptolithina within the class Pterobranchia. These filter-feeding organisms are known chiefly from f ...
'' (a genus of biserial graptolites).
Graptolite fossils were later referred to a variety of groups, including other branching colonial animals such as
bryozoans
Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about long, they have a special feeding structure called a l ...
("moss animals") and
hydrozoans
Hydrozoa (hydrozoans; ) are a taxonomic class of individually very small, predatory animals, some solitary and some colonial, most of which inhabit saline water. The colonies of the colonial species can be large, and in some cases the specialized ...
. The term Graptolithina was established by Bronn in 1849, who considered them to represent
orthoconic
An orthocone is an unusually long straight shell of a nautiloid cephalopod.; During the 18th and 19th centuries, all shells of this type were named '' Orthoceras'', creating a wastebasket taxon, but it is now known that many groups of nautiloids ...
cephalopods. By the mid-20th century, graptolites were recognized as a unique group closely related to living pterobranchs in the genera ''
Rhabdopleura
''Rhabdopleura'' is a genus of colonial sessile hemichordates belonging to the Pterobranchia class. As one of the oldest living genera with a fossil record dating back to the Middle Cambrian, it is also considered to be the only living genus of ...
'' and ''
Cephalodiscus
''Cephalodiscus'' is a genus of hemichordates in the monotypic family Cephalodiscidae of the order Cephalodiscida.
Description
Unlike ''Rhabdopleura'', ''Cephalodiscus'' species do not form large colonies and are only pseudocolonial. ''Cephalod ...
'', which had been described in the late 19th century. ''Graptolithus'', as a genus, was officially abandoned in 1954 by the
ICZN
The International Code of Zoological Nomenclature (ICZN) is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals. It is also informally known as the ICZN Code, for its publisher, the I ...
.
[Bulman, M. (1970) ''In'' Teichert, C. (ed.). '']Treatise on Invertebrate Paleontology
The ''Treatise on Invertebrate Paleontology'' (or ''TIP'') published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and co ...
. Part V. Graptolithina, with sections on Enteropneusta and Pterobranchia''. (2nd Edition). Geological Society of America and University of Kansas Press, Boulder, Colorado and Lawrence, Kansas, XXXII + 163 pp.
Morphology
Colony structure
![Rhabdopleuratubes](https://upload.wikimedia.org/wikipedia/commons/2/20/Rhabdopleuratubes.png)
Each graptolite colony originates from an initial individual, called the sicular zooid, from which the subsequent
zooids
A zooid or zoöid is a single animal that is part of a colonial animal. This lifestyle has been adopted by animals from separate unrelated taxa. Zooids are multicellular; their structure is similar to that of other solitary animals. The zooi ...
will develop. They are all interconnected by
stolons
In biology, stolons (from Latin '' stolō'', genitive ''stolōnis'' – "branch"), also known as runners, are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are external s ...
, a true colonial system shared by ''Rhabdopleura'' but not ''Cephalodiscus''. These zooids are housed within an organic structure comprising a series of tubes secreted by the glands on the
cephalic shield. The colony structure has been known from several different names, including coenecium (for living pterobranchs), rhabdosome (for fossil graptolites), and most commonly tubarium (for both). The individual tubes, each occupied by a single zooid, are known as
theca
In biology, a theca (plural thecae) is a sheath or a covering.
Botany
In botany, the theca is related to plant's flower anatomy. The theca of an angiosperm consists of a pair of microsporangia that are adjacent to each other and share a commo ...
.
The composition of the tubarium is not clearly known, but different authors suggest it is made out of
collagen
Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whole ...
or
chitin
Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chit ...
. In some colonies, there are two sizes of theca, the larger autotheca and smaller bitheca, and it has been suggested that this difference is due to
sexual dimorphism
Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...
of zooids within a colony.
Early in the development of a colony, the tubarium splits into a variable number of branches (known as stipes) and different arrangements of the theca, features which are important in the identification of graptolite fossils. Colonies can be classified by their total number of theca rows (biserial colonies have two rows, uniserial have one) and the number of initial stipes per colony (multiramous colonies have many stipes, pauciramous colonies have two or fewer). Each thecal tube is mostly made up by two series of stacked semicircular half-rings, known as fuselli (sing: fusellum). The fuselli resemble growth lines when preserved in fossils, and the two stacks meet along a suture with a zig-zag pattern. Fuselli are the major reinforcing component of a tubarium, though they are assisted by one or more additional layers of looser tissue, the cortex.
The earliest graptolites appeared in the fossil record during the Cambrian, and were generally
sessile
Sessility, or sessile, may refer to:
* Sessility (motility), organisms which are not able to move about
* Sessility (botany), flowers or leaves that grow directly from the stem or peduncle of a plant
* Sessility (medicine), tumors and polyps that ...
animals, with a colony attached to the sea floor. Several early-diverging families were encrusting organisms, with the colony developing horizontally along a substrate. Extant ''Rhabdopleura'' fall into this category, with an overall encrusting colony form combined with erect, vertical theca. Most of the erect, dendritic or bushy/fan-shaped graptolites are classified as dendroids (order Dendroidea). Their colonies were attached to a hard substrate by their own weight via an attachment disc. Graptolites with relatively few branches were derived from the dendroid graptolites at the beginning of the
Ordovician
The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start ...
period. This latter major group, the graptoloids (order Graptoloidea) were
pelagic
The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or wa ...
and
planktonic
Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...
, drifting freely through the water column. They were a successful and prolific group, being the most important and widespread macroplanktonic animals until they died out in the early part of the
Devonian
The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...
period. The dendroid graptolites survived until the
Carboniferous
The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...
period.
Zooid morphology
![Zooidgrap](https://upload.wikimedia.org/wikipedia/commons/7/72/Zooidgrap.jpg)
A mature zooid has three important regions, the preoral disc or cephalic shield, the collar and the trunk. In the collar, the mouth and anus (U-shaped digestive system) and arms are found; Graptholitina has a single pair of arms with several paired tentacles. As a
nervous system
In biology, the nervous system is the highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body. The nervous system detects environmental changes th ...
, graptolites have a simple layer of fibers between the epidermis and the basal lamina, also have a ''collar ganglion'' that gives rise to several nerve branches, similar to the
neural tube
In the developing chordate (including vertebrates), the neural tube is the embryonic precursor to the central nervous system, which is made up of the brain and spinal cord. The neural groove gradually deepens as the neural fold become elevated, a ...
of chordates.
All this information was inferred by the extant ''
Rhabdopleura
''Rhabdopleura'' is a genus of colonial sessile hemichordates belonging to the Pterobranchia class. As one of the oldest living genera with a fossil record dating back to the Middle Cambrian, it is also considered to be the only living genus of ...
'', however, it is very likely that fossil zooids had the same morphology.
Taxonomy
Since the 1970s, as a result of advances in
electron microscopy
An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination. As the wavelength of an electron can be up to 100,000 times shorter than that of visible light photons, electron microscopes have a hi ...
, graptolites have generally been thought to be most closely allied to the
pterobranch
Pterobranchia is a Class (biology), class of small worm-shaped animals. They belong to the Hemichordata, and live in secretion, secreted tubes on the ocean floor. Pterobranchia feed by filtering plankton out of the water with the help of cilia a ...
s, a rare group of modern marine animals belonging to the phylum
Hemichordata.
Comparisons are drawn with the modern hemichordates ''
Cephalodiscus
''Cephalodiscus'' is a genus of hemichordates in the monotypic family Cephalodiscidae of the order Cephalodiscida.
Description
Unlike ''Rhabdopleura'', ''Cephalodiscus'' species do not form large colonies and are only pseudocolonial. ''Cephalod ...
'' and ''
Rhabdopleura
''Rhabdopleura'' is a genus of colonial sessile hemichordates belonging to the Pterobranchia class. As one of the oldest living genera with a fossil record dating back to the Middle Cambrian, it is also considered to be the only living genus of ...
''. According to recent phylogenetic studies, rhabdopleurids are placed within the Graptolithina. Nonetheless, they are considered an ''
incertae sedis
' () or ''problematica'' is a term used for a taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty ...
'' family.
On the other hand,
Cephalodiscida is considered to be a sister subclass of Graptolithina. One of the main differences between these two groups is that Cephalodiscida species are not a colonial organisms. In Cephalodiscida organisms, there is no common canal connecting all zooids. Cephalodiscida zooids have several arms, while Graptolithina zooids have only one pair of arms. Other differences include the type of early development, the gonads, the presence or absence of
gill slits
Gill slits are individual openings to gills, i.e., multiple gill arches, which lack a single outer cover. Such gills are characteristic of Chondrichthyes, cartilaginous fish such as sharks and Batoidea, rays, as well as deep-branching vertebrates ...
, and the size of the zooids. However, in the fossil record where mostly tubaria (tubes) are preserved, it is complicated to distinguish between groups.
Graptolithina includes several minor families as well as two main extinct orders, Dendroidea (
benthic
The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...
graptolites) and Graptoloidea (
planktic
Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a cruc ...
graptolites). The latter is the most diverse, including 5 suborders, where the most assorted is Axonophora (biserial graptolites, etc.). This group includes Diplograptids and Neograptids, groups that had a great development during the Ordovician.
Old taxonomic classifications consider the orders Dendroidea, Tuboidea, Camaroidea, Crustoidea, Stolonoidea, Graptoloidea, and Dithecoidea but new classifications embedded them into Graptoloidea at different taxonomic levels.
Taxonomy of Graptolithina by Maletz (2014):
Subclass Graptolithina Bronn, 1849
*''Incertae sedis
' () or ''problematica'' is a term used for a taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty ...
''
**Family Rhabdopleuridae
Rhabdopleurida is one of three orders in the class Pterobranchia, which are small, worm-shaped animals, are the only surviving graptolites. Members belong to the hemichordates. Species in this order are sessile, colonial, connected with a st ...
Harmer, 1905
**Family †Cysticamaridae
Cysticamaridae is an extinct family of graptolite
Graptolites are a group of colonial animals, members of the subclass Graptolithina within the class Pterobranchia. These filter-feeding organisms are known chiefly from fossils found from t ...
Bulman, 1955
**Family †Wimanicrustidae
Wimanicrustidae is an extinct family of graptolite
Graptolites are a group of colonial animals, members of the subclass Graptolithina within the class Pterobranchia. These filter-feeding organisms are known chiefly from fossils found from ...
Bulman, 1970
**Family †Dithecodendridae
Dithecodendridae is an extinct family of graptolite
Graptolites are a group of colonial animals, members of the subclass Graptolithina within the class Pterobranchia. These filter-feeding organisms are known chiefly from fossils found from ...
Obut, 1964
**Family †Cyclograptidae
Cyclograptidae is an extinct family of graptolite
Graptolites are a group of colonial animals, members of the subclass Graptolithina within the class Pterobranchia. These filter-feeding organisms are known chiefly from fossils found from t ...
Bulman, 1938
*Order †Dendroidea
Graptolites are a group of Colony (biology)#Modular organisms, colonial animals, members of the subclass Graptolithina within the class (biology), class Pterobranchia. These Filter feeder, filter-feeding organisms are known chiefly from fossils ...
Nicholson, 1872
**Family † Dendrograptidae Roemer, 1897 in Frech, 1897
**Family † Acanthograptidae Bulman, 1938
**Family † Mastigograptidae Bates & Urbanek, 2002
*Order †Graptoloidea
Graptolites are a group of colonial animals, members of the subclass Graptolithina within the class Pterobranchia. These filter-feeding organisms are known chiefly from fossils found from the Middle Cambrian (Miaolingian, Wuliuan) through the L ...
Lapworth, 1875 in Hopkinson & Lapworth, 1875 (planktic graptolites)
**Suborder † Graptodendroidina Mu & Lin, 1981 in Lin (1981)
***Family † Anisograptidae Bulman, 1950
**Suborder † Sinograpta Maletz et al., 2009
***Family † Sigmagraptidae Cooper & Fortey, 1982
***Family † Sinograptidae Mu, 1957
***Family † Abrograptidae Mu, 1958
**Suborder † Dichograptina Lapworth, 1873
***Family † Dichograptidae Lapworth, 1873
***Family † Didymograptidae Mu, 1950
***Family † Pterograptidae Mu, 1950
***Family †Tetragraptidae
Tetragraptidae is an extinct family of graptolites from the Floian to Darriwilian epochs of the Ordovician Period.
Genera
List of genera from Maletz (2014):
*†''Corymbograptus'' Obut & Sobolevskaya, 1964
*†''Paratetragraptus'' Obut, 1957
* ...
Frech, 1897
**Suborder † Glossograptina Jaanusson, 1960
***Family † Isograptidae Harris, 1933
***Family † Glossograptidae Lapworth, 1873
**Suborder † Axonophora Frech, 1897 (biserial graptolites, and also retiolitids and monograptids)
***Infraorder † Diplograptina Lapworth, 1880
****Family † Diplograptidae Lapworth, 1873
*****Subfamily † Diplograptinae Lapworth, 1873
*****Subfamily † Orthograptinae Mitchell, 1987
****Family † Lasiograptidae Lapworth, 1880e
****Family † Climacograptidae Frech, 1897
****Family † Dicranograptidae Lapworth, 1873
*****Subfamily † Dicranograptinae Lapworth, 1873
*****Subfamily † Nemagraptinae Lapworth, 1873
***Infraorder † Neograptina Štorch et al., 2011
****Family † Normalograptidae Štorch & Serpagli, 1993
****Family † Neodiplograptidae Melchin et al., 2011
*****Subfamily † Neodiplograptinae Melchin et al. 2011
*****Subfamily † Petalolithinae Bulman, 1955
****Superfamily † Retiolitoidea Lapworth, 1873
*****Family † Retiolitidae Lapworth, 1873
******Subfamily † Retiolitinae Lapworth, 1873
******Subfamily † Plectograptinae Bouček & Münch, 1952
****Superfamily † Monograptoidea Lapworth, 1873
*****Family † Dimorphograptidae Elles & Wood, 1908
*****Family † Monograptidae Lapworth, 1873
Ecology
Graptolites were a major component of the early Paleozoic
The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon.
The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838
by combining the Greek words ''palaiós'' (, "old") and ' ...
ecosystems, especially for the zooplankton
Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...
because the most abundant and diverse species were planktonic. Graptolites were most likely suspension feeders and strained the water for food such as plankton.
Inferring by analogy with modern pterobranchs, they were able to migrate vertically through the water column for feeding efficiency and to avoid predators. With ecological models and studies of the facies
In geology, a facies ( , ; same pronunciation and spelling in the plural) is a body of rock with specified characteristics, which can be any observable attribute of rocks (such as their overall appearance, composition, or condition of formatio ...
, it was observed that, at least for Ordovician species, some groups of species are largely confined to the epipelagic
The photic zone, euphotic zone, epipelagic zone, or sunlight zone is the uppermost layer of a body of water that receives sunlight, allowing phytoplankton to perform photosynthesis. It undergoes a series of physical, chemical, and biological proc ...
and mesopelagic
The mesopelagic zone (Greek μέσον, middle), also known as the middle pelagic or twilight zone, is the part of the pelagic zone that lies between the photic epipelagic and the aphotic bathypelagic zones. It is defined by light, and begins ...
zone, from inshore to open ocean.[Cooper, R., Rigby, S., Loydell, D. & Bates, D. (2012) Palaeoecology of the Graptoloidea. ''Earth-Science Reviews'', 112(1):23-41.] Living rhabdopleura have been found in deep waters in several regions of Europe and America but the distribution might be biased by sampling efforts; colonies are usually found as epibiont
An epibiont (from the Ancient Greek meaning "living on top of") is an organism that lives on the surface of another living organism, called the basibiont ("living underneath"). The interaction between the two organisms is called epibiosis. An epi ...
s of shells.
Their locomotion was relative to the water mass in which they lived but the exact mechanisms (such as turbulence, buoyancy
Buoyancy (), or upthrust, is an upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus the p ...
, active swimming, and so forth) are not clear yet. One proposal, put forward by Melchin and DeMont (1995), suggested that graptolite movement was analogous to modern free-swimming animals with heavy housing structures. In particular, they compared graptolites to "sea butterflies" ( Thecostomata), small swimming pteropod snails
A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class Gastrop ...
. Under this suggestion, graptolites moved through rowing
Rowing is the act of propelling a human-powered watercraft using the sweeping motions of oars to displace water and generate reactional propulsion. Rowing is functionally similar to paddling, but rowing requires oars to be mechanically atta ...
or swimming via an undulatory movement of paired muscular appendages
An appendage (or outgrowth) is an external body part, or natural prolongation, that protrudes from an organism's body.
In arthropods, an appendage refers to any of the homologous body parts that may extend from a body segment, including anten ...
developed from the cephalic shield or feeding tentacles. However, in some species, the thecal aperture was probably so restricted that the appendages hypothesis is not feasible. On the other hand, buoyancy is not supported by any extra thecal tissue or gas build-up control mechanism, and active swimming requires a lot of energetic waste, which would rather be used for the tubarium construction.
There are still many questions regarding graptolite locomotion but all these mechanisms are possible alternatives depending on the species and its habitat. For benthic species, that lived attached to the sediment or any other organism, this was not a problem; the zooids were able to move but restricted within the tubarium. Although this zooid movement is possible in both planktic and benthic species, it is limited by the stolon
In biology, stolons (from Latin '' stolō'', genitive ''stolōnis'' – "branch"), also known as runners, are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are external s ...
but is particularly useful for feeding. Using their arms and tentacles, which are close to the mouth, they filter the water to catch any particles of food.
Life cycle
The study of the developmental biology
Developmental biology is the study of the process by which animals and plants grow and develop. Developmental biology also encompasses the biology of Regeneration (biology), regeneration, asexual reproduction, metamorphosis, and the growth and di ...
of Graptholitina has been possible by the discovery of the species ''R. compacta'' and '' R. normani'' in shallow waters; it is assumed that graptolite fossils had a similar development as their extant representatives. The life cycle comprises two events, the ontogeny
Ontogeny (also ontogenesis) is the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the egg to adult. The term can also be used to refer to the stu ...
and the astogeny, where the main difference is whether the development is happening in the individual organism or in the modular
Broadly speaking, modularity is the degree to which a system's components may be separated and recombined, often with the benefit of flexibility and variety in use. The concept of modularity is used primarily to reduce complexity by breaking a sy ...
growth of the colony.
The life cycle begins with a planktonic planula-like larva
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
The ...
produced by sexual reproduction, which later becomes the ''sicular zooid'' who starts a colony. In ''Rhabdopleura
''Rhabdopleura'' is a genus of colonial sessile hemichordates belonging to the Pterobranchia class. As one of the oldest living genera with a fossil record dating back to the Middle Cambrian, it is also considered to be the only living genus of ...
'', the colonies bear male and female zooids but fertilized eggs are incubated in the female tubarium, and stay there until they become larvae able to swim (after 4–7 days) to settle away to start a new colony. Each larva surrounds itself in a protective cocoon where the metamorphosis to the zooid takes place (7–10 days) and attaches with the posterior part of the body, where the stalk will eventually develop.
The development is indirect and lecithotrophic
Oviparous animals are animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, most reptiles, and all pterosaurs, dinosaurs (including birds), and mo ...
, and the larvae are ciliated and pigmented, with a deep depression on the ventral side.[Sato, A., Bishop, J. & Holland, P. (2008). Developmental Biology of Pterobranch Hemichordates: History and Perspectives. ''Genesis'', 46:587-591.] Astogeny happens when the colony grows through asexual reproduction
Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the fu ...
from the tip of a permanent terminal zooid, behind which the new zooids are budded from the stalk, a type of budding called monopodial
Vascular plants with monopodial growth habits grow upward from a single point. They add leaves to the apex each year and the stem grows longer accordingly. The word ''Monopodial'' is derived from Greek "mono-", ''one'' and "podial", "foot", in refe ...
. It is possible that in graptolite fossils the terminal zooid was not permanent because the new zooids formed from the tip of latest one, in other words, sympodial
Sympodial growth is a bifurcating branching pattern where one branch develops more strongly than the other, resulting in the stronger branches forming the primary shoot and the weaker branches appearing laterally. A sympodium, also referred to a ...
budding. These new organisms break a hole in the tubarium wall and start secreting their own tube.
Graptolites in evolutionary development
In recent years, living graptolites have been used as a hemichordate model for Evo-Devo
Evolutionary developmental biology (informally, evo-devo) is a field of biological research that compares the developmental processes of different organisms to infer how developmental processes evolved.
The field grew from 19th-century beginni ...
studies, as have their sister group, the acorn worms
The acorn worms or Enteropneusta are a hemichordate class of invertebrates consisting of one order of the same name. The closest non-hemichordate relatives of the Enteropneusta are the echinoderms. There are 111 known species of acorn worm in th ...
. For example, graptolites are used to study asymmetry in hemichordates, especially because their gonads tend to be located randomly on one side. In ''Rhabdopleura normani
''Rhabdopleura normani'' is a small, marine species of worm-shaped animal known as a pterobranch. It is a sessile suspension feeder, lives in clear water, and secretes tubes on the ocean floor.
Description
This species grows in colonies. Each ...
'', the testicle
A testicle or testis (plural testes) is the male reproductive gland or gonad in all bilaterians, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testostero ...
is located asymmetrically, and possibly other structures such as the oral lamella and the gonopore
A gonopore, sometimes called a gonadopore, is a genital pore in many invertebrates. Hexapods, including insects have a single common gonopore, except mayflies, which have a pair of gonopores. More specifically, in the unmodified female it is the ...
.[Sato, A. & Holland, P. (2008). Asymmetry in a Pterobranch Hemichordate and the Evolution of Left-Right Patterning. ''Developmental Dynamics'', 237:3634 –3639)] The significance of these discoveries is to understand the early vertebrate left-right asymmetry
Asymmetry is the absence of, or a violation of, symmetry (the property of an object being invariant to a transformation, such as reflection). Symmetry is an important property of both physical and abstract systems and it may be displayed in pre ...
due to chordates
A chordate () is an animal of the phylum Chordata (). All chordates possess, at some point during their larval or adult stages, five synapomorphies, or primary physical characteristics, that distinguish them from all the other taxa. These five ...
being a sister group of hemichordates, and therefore, the asymmetry might be a feature that developed early in deuterostomes
Deuterostomia (; in Greek) are animals typically characterized by their anus forming before their mouth during embryonic development. The group's sister clade is Protostomia, animals whose digestive tract development is more varied. Some exampl ...
. Since the location of the structures is not strictly established, also in some enteropneusts, it is likely that asymmetrical states in hemichordates are not under a strong developmental or evolutionary constraint. The origin of this asymmetry, at least for the gonads, is possibly influenced by the direction of the basal coiling in the tubarium, by some intrinsic biological mechanisms in pterobranchs, or solely by environmental factors.
''Hedgehog
A hedgehog is a spiny mammal of the subfamily Erinaceinae, in the eulipotyphlan family Erinaceidae. There are seventeen species of hedgehog in five genera found throughout parts of Europe, Asia, and Africa, and in New Zealand by introducti ...
'' (hh), a highly conserved gene implicated in neural developmental patterning, was analyzed in Hemichordates, taking ''Rhabdopleura'' as a pterobranch representative. It was found that hedgehog gene in pterobranchs is expressed in a different pattern compared to other hemichordates as the enteropneust ''Saccoglossus kowalevskii
Hemichordata is a phylum which consists of triploblastic, enterocoelomate, and bilaterally symmetrical marine deuterostome animals, generally considered the sister group of the echinoderms. They appear in the Lower or Middle Cambrian and incl ...
''. An important conserved glycine–cysteine–phenylalanine (GCF) motif at the site of autocatalytic cleavage in hh genes, is altered in ''R. compacta'' by an insertion of the amino acid
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...
threonine
Threonine (symbol Thr or T) is an amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH form under biological conditions), a carboxyl group (which is in the deprotonated −COO ...
(T) in the N-terminal, and in ''S. kowalesvskii'' there is a replacement of serine
Serine (symbol Ser or S) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated − form under biological conditions), a carboxyl group (which is in the deprotonated − form un ...
(S) for glycine
Glycine (symbol Gly or G; ) is an amino acid that has a single hydrogen atom as its side chain. It is the simplest stable amino acid (carbamic acid is unstable), with the chemical formula NH2‐ CH2‐ COOH. Glycine is one of the proteinogeni ...
(G). This mutation decreases the efficiency of the autoproteolytic cleavage and therefore, the signalling function of the protein. It is not clear how this unique mechanism occurred in evolution and the effects it has in the group, but, if it has persisted over millions of years, it implies a functional and genetic advantage.[Sato, A., White-Cooper, H., Doggett, K. & Holland, P. 2009. Degenerate evolution of the hedgehog gene in a hemichordate lineage. ''Proceedings of the National Academy of Sciences'', 106(18):7491-7494.]
Geological relevance
Preservation
Graptolites are common fossils and have a worldwide distribution. They are most commonly found in shale
Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...
s and mudrocks where sea-bed fossils are rare, this type of rock having formed from sediment
Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand an ...
deposited in relatively deep water that had poor bottom circulation, was deficient in oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
, and had no scavengers. The dead planktic graptolites, having sunk to the sea floor, would eventually become entombed in the sediment and were thus well preserved.
These colonial animals are also found in limestone
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...
s and chert
Chert () is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a prec ...
s, but generally these rocks were deposited in conditions which were more favorable for bottom-dwelling life, including scavengers, and undoubtedly most graptolite remains deposited here were generally eaten by other animals.
Fossils are often found flattened along the bedding plane of the rocks in which they occur, though may be found in three dimensions when they are infilled by iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
pyrite
The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Iron, FeSulfur, S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral.
Pyrite's metallic Luster (mineralogy), lust ...
or some other minerals. They vary in shape, but are most commonly dendritic
Dendrite derives from the Greek word "dendron" meaning ( "tree-like"), and may refer to:
Biology
*Dendrite, a branched projection of a neuron
*Dendrite (non-neuronal), branching projections of certain skin cells and immune cells
Physical
* Dendr ...
or branching (such as ''Dictyonema
''Dictyonema'' is a genus of mainly tropical basidiolichens in the family Hygrophoraceae.
The ''Dictyonema'' symbiosis
Most lichens are a symbiosis between an ascomycete fungus and a photosynthetic green alga. However, a small percentage of ...
''), sawblade
A saw is a tool consisting of a tough blade, wire, or chain with a hard toothed edge. It is used to cut through material, very often wood, though sometimes metal or stone. The cut is made by placing the toothed edge against the material and mo ...
-like, or "tuning fork
A tuning fork is an acoustic resonator in the form of a two-pronged fork with the prongs (tines) formed from a U-shaped bar of elastic metal (usually steel). It resonates at a specific constant pitch when set vibrating by striking it against ...
"-shaped (such as ''Didymograptus
''Didymograptus'' is an extinct genus of graptolites with four rows of cups. They lived during the Middle Ordovician, to Late Ordovician
The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The ...
murchisoni''). Their remains may be mistaken for fossil plant
Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclud ...
s by the casual observer, as it has been the case for the first graptolite descriptions.
Graptolites are normally preserved as a black carbon film {{distinguish, Carbonaceous film (paleontology)
Carbon films are thin film coatings which consist predominantly of the chemical element carbon. They include plasma polymer films, amorphous carbon films ( diamond-like carbon, DLC), CVD diamond films ...
on the rock's surface or as light grey clay films in tectonically
Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents k ...
distorted rocks. The fossil can also appear stretched or distorted. This is due to the strata that the graptolite is within, being folded and compacted. They may be sometimes difficult to see, but by slanting the specimen to the light they reveal themselves as a shiny marking. Pyritized
Permineralization is a process of fossilization of bones and tissues in which mineral deposits form internal casts of organisms. Carried by water, these minerals fill the spaces within organic tissue. Because of the nature of the casts, perminera ...
graptolite fossils are also found.
A well-known locality for graptolite fossils in Britain is Abereiddy Bay
Abereiddy ( cy, Abereddi) is a hamlet in the county of Pembrokeshire, in west Wales.
It has a small beach which was awarded the Blue flag rural beach award in 2005. A large car park adjoins the beach, where in the summer an ice cream van can u ...
, Dyfed
Dyfed () is a preserved county in southwestern Wales. It is a mostly rural area with a coastline on the Irish Sea and the Bristol Channel.
Between 1974 and 1996, Dyfed was also the name of the area's county council and the name remains in use f ...
, Wales
Wales ( cy, Cymru ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by England to the Wales–England border, east, the Irish Sea to the north and west, the Celtic Sea to the south west and the ...
, where they occur in rocks from the Ordovician Period
The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya.
The ...
. Sites in the Southern Uplands
The Southern Uplands ( gd, Na Monaidhean a Deas) are the southernmost and least populous of mainland Scotland's three major geographic areas (the other two being the Central Lowlands and the Grampian Mountains and the Highlands, as illustrated ...
of Scotland, the Lake District
The Lake District, also known as the Lakes or Lakeland, is a mountainous region in North West England. A popular holiday destination, it is famous for its lakes, forests, and mountains (or ''fells''), and its associations with William Wordswor ...
and Welsh Borders
The Welsh Marches ( cy, Y Mers) is an imprecisely defined area along the border between England and Wales in the United Kingdom. The precise meaning of the term has varied at different periods.
The English term Welsh March (in Medieval Latin ...
also yield rich and well-preserved graptolite faunas. A famous graptolite location in Scotland is Dob's Linn
Dob's Linn is a small steep valley in Dumfries and Galloway, just north of the A708 road between Moffat and Selkirk, in Scotland. It is part of the Grey Mare's Tail Nature Reserve which is owned by the National Trust for Scotland. According to ...
with species from the boundary Ordovician-Silurian. However, since the group had a wide distribution, they are also abundantly found in several localities in the United States, Canada, Australia, Germany, China, among others.
Stratigraphy
Graptolite fossils have predictable preservation, widespread distribution, and gradual change over a geologic time scale
The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochrono ...
. This allows them to be used to date strata
In geology and related fields, a stratum ( : strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as ei ...
of rocks throughout the world. They are important index fossils
Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them.Hine, Robert. “Biostratigraphy.” ''Oxford Reference: Dictionary of Bi ...
for dating Palaeozoic
The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon.
The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838
by combining the Greek words ''palaiós'' (, "old") and '' ...
rocks as they evolved rapidly with time and formed many different distinctive species. Geologists can divide the rocks of the Ordovician
The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start ...
and Silurian
The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...
periods into graptolite biozones; these are generally less than one million years in duration. A worldwide ice age
An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gree ...
at the end of the Ordovician eliminated most graptolites except the neograptines. Diversification from the neograptines that survived the Ordovician glaciation
A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate betw ...
began around 2 million years later.[Bapst, D., Bullock, P., Melchin, M., Sheets, D. & Mitchell, C. (2012) Graptoloid diversity and disparity became decoupled during the Ordovician mass extinction. ''Proceedings of the National Academy of Sciences'', 109(9):3428-3433.]
The Great Ordovician Biodiversification Event
The Great Ordovician Biodiversification Event (GOBE), was an evolutionary radiation of animal life throughout the Ordovician period, 40 million years after the Cambrian explosion, whereby the distinctive Cambrian fauna fizzled out to be replaced wi ...
( GOBE) influenced changes in the morphology of the colonies and thecae, giving rise to new groups like the planktic Graptoloidea. Later, some of the greatest extinctions that affected the group were the Hirnantian
The Hirnantian is the final internationally recognized stage of the Ordovician Period of the Paleozoic Era. It was of short duration, lasting about 1.4 million years, from to Ma (million years ago). The early part of the Hirnantian was charact ...
in the Ordovician and the Lundgreni in the Silurian, where graptolite populations were dramatically reduced (see also Lilliput effect).
Researchers
The following is a selection of graptolite and pterobranch researchers:
*Joachim Barrande
Joachim Barrande (11 August 1799 – 5 October 1883) was a French geologist and palaeontologist.
Career
Barrande was born at Saugues, Haute Loire, and educated in the École Polytechnique and École Nationale des Ponts et Chaussées at Paris. Al ...
(1799–1883)
*Hanns Bruno Geinitz
Hanns Bruno Geinitz (16 October 1814 – 28 January 1900) was a German geologist, born at Altenburg, the capital of Saxe-Altenburg.
He was educated at the universities of Berlin and Jena, and gained the foundations of his geological knowledge ...
(1814–1900)
* James Hall (1811–1898)
* Frederick M'Coy (1817–1899)
*Henry Alleyne Nicholson
Henry Alleyne Nicholson FRS FRSE FGS FLS (11 September 1844 – 19 January 1899) was a British palaeontologist and zoologist.
Life
The son of John Nicholson (1809–1886), a biblical scholar, and his wife Annie Elizabeth Waring, he was born a ...
(1844–1899)
*John Hopkinson
John Hopkinson, FRS, (27 July 1849 – 27 August 1898) was a British physicist, electrical engineer, Fellow of the Royal Society and President of the IEE (now the IET) twice in 1890 and 1896. He invented the three-wire (three-phase) system for ...
(1844–1919)
* Sven Leonhard Törnquist (1840–1920)
* Sven Axel Tullberg (1852–1886)
* Gerhard Holm (1853–1926)
*Carl Wiman
Carl Johan Josef Ernst Wiman (March 10, 1867 – June 15, 1944) was a Swedish palaeontologist, the first professor of palaeontology and historical geology at Uppsala University, and the father of Swedish vertebrate palaeontology.
Wiman was ...
(1867–1944)
* Thomas Sergeant Hall (1858–1915)
* Alexander Robert Keble (1884–1963)
*Noel Benson
William Noel Benson FRS FRGS (26 December 1885 – 20 August 1957) was an English-born research geologist and academic active first in Australia and then New Zealand. After studying geology at the University of Sydney, Benson worked temporari ...
(1885–1957)
* William John Harris (1886–1957)
* David Evan Thomas (1902–1978)
* Mu Enzhi (1917–1987)
*Li Jijin
Li, li, or LI may refer to:
Businesses and organizations
* Landscape Institute, a British professional body for landscape architects
* Leadership Institute, a non-profit organization located in Arlington, Virginia, US, that teaches "political tec ...
(1928–2013)
*Vladimir Nikolayevich Beklemishev
Vladimir Nikolayevich Beklemishev (russian: Владимир Николаевич Беклемишев; , Hrodna4 September 1962, Moscow) was a Russian zoologist and entomologist.
Beklemishev began his career at Saint Petersburg University. In 1 ...
(1890–1962)
*Michael Sars
Michael Sars (30 August 1805 – 22 October 1869) was a Norwegian theologian and biologist.
Biography
Sars was born in Bergen, Norway. He studied natural history and theology at Royal Frederick University from 1823 and completed a cand.theol. de ...
(1805–1869)
* George Ossian Sars (1837–1927)
* William Carmichael M'Intosh (1838–1931)
* Nancy Kirk (1916–2005)
*Roman Kozłowski
Roman Stanisław Jakub Kozłowski (1 February 1889 – 2 May 1977) was a Polish palaeontologist, best known for his work on graptolites.
Kozłowski was born in Włocławek, north-west of Warsaw, on 1 February 1889. He studied at universities in Sw ...
(1889–1977)
*Jörg Maletz Jörg or Joerg () is a German name, equivalent to George in English.
* Jörg Bergmeister, German race car driver
* Jörg Frischmann, German Paralympian athlete
* Jörg Haider, Austrian politician
* Jörg Andrees Elten (also Swami Satyananda), Germ ...
* Denis E. B. Bates
* Alfred C. Lenz
* Chris B. Cameron
* Adam Urbanek
* David K. Loydell
*Hermann Jaeger (1929–1992)
See also
*List of graptolite genera
This list of graptolites is an attempt to create a comprehensive listing of all Genus, genera from the fossil record that have ever been considered to be members of Graptolithina, excluding purely vernacular terms. The list includes all commonly a ...
References
External links
*Classification of the Graptolithoidea
Graptolites and Pterobranchs
*Podcast on Graptolites by David Bapst
Palaeocast
*Graptolites gallery by Michael P. Klimetz
*What are Fossil Graptolites and why are they useful in geology?
Youtube
*Writing on the rocks
Stephen Hui Geological Museum
{{Authority control
Prehistoric deuterostome classes
Paleozoic invertebrates
Cambrian invertebrates
Carboniferous invertebrates
Devonian invertebrates
Ordovician invertebrates
Permian invertebrates
Silurian invertebrates
Cambrian first appearances
Carboniferous extinctions