''Stanleycaris'' is an
extinct
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
,
monotypic
In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of
hurdiid
Hurdiidae is an extinct cosmopolitan family of radiodonts, a group of stem-group arthropods, which lived during the Paleozoic Era. It is the most long-lived radiodont clade, lasting from the Cambrian period to the Devonian period.
Descripti ...
radiodont
Radiodonta is an extinct Order (biology), order of stem-group arthropods that was successful worldwide during the Cambrian period. They may be referred to as radiodonts, radiodontans, radiodontids, anomalocarids, or anomalocaridids, although the ...
from the middle
Cambrian
The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ...
(Miaolingian). The
type species
In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...
is ''Stanleycaris hirpex''. ''Stanleycaris'' was described from the
Stephen Formation
The Stephen Formation is a geologic formation exposed in the Canadian Rockies of British Columbia and Alberta, on the western edge of the Western Canada Sedimentary Basin. It consists of shale, thin-bedded limestone, and siltstone that was deposite ...
near the
Stanley Glacier
The Stanley Glacier locality in British Columbia is an exposure of the "thin" Stephen formation exhibiting soft-tissue preservation. Fossils were discovered by a hiker who reported the find to Parks Canada; this brought the site to the attention ...
and
Burgess Shale
The Burgess Shale is a fossil-bearing deposit exposed in the Canadian Rockies of British Columbia, Canada. It is famous for the exceptional preservation of the soft parts of its fossils. At old (middle Cambrian), it is one of the earliest foss ...
locality of
Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
,
as well as
Wheeler Formation
The Wheeler Shale (named by Charles Walcott) is a Cambrian ( 507 Ma) fossil locality world-famous
for prolific agnostid and ''Elrathia kingii'' trilobite remains (even though many areas are barren of fossils)
and represents a Konzent ...
of
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
.
The genus was characterized by the
rake
Rake may refer to:
* Rake (stock character), a man habituated to immoral conduct
* Rake (theatre), the artificial slope of a theatre stage
Science and technology
* Rake receiver, a radio receiver
* Rake (geology), the angle between a feature on a ...
-like
frontal appendages with robust inner spines.
''Stanleycaris'' was originally described only from frontal appendages and oral cone.
However, in 2022, 268 specimens of ''Stanleycaris'', many of which were complete, were studied, making ''Stanleycaris'' a well documented radiodont.
''Stanleycaris'' had three eyes, a bizarre configuration previously unknown among other radiodont genera; yet this head anatomy supports early differentiation among arthropod head and trunk segmentation.
The original description of the taxon appeared in an online supplement to the article published by
Jean-Bernard Caron,
Robert R. Gaines
Robert Riepma Gaines (born 1973) is an American geologist who teaches at Pomona College in Claremont, California. From July 2019 to June 2022, he served as the Vice President of Academic Affairs and Dean of the college. He is known for his resea ...
, M. Gabriela Mángano, Michael Streng and Allison C. Daley in
2010
File:2010 Events Collage New.png, From top left, clockwise: The 2010 Chile earthquake was one of the strongest recorded in history; The Eruption of Eyjafjallajökull in Iceland disrupts air travel in Europe; A scene from the opening ceremony of ...
.
That description did not satisfy of the requirements of the
International Code of Zoological Nomenclature
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 ...
, as the Code did not accept taxa named in electronic publications as validly named until 2012;
the name was eventually validated by Pates, Daley & Ortega-Hernández (2018).
Etymology
Its generic name means "Crab of Stanley Glacier"; ''hirpex'', L. "large rake", reflects the
rake
Rake may refer to:
* Rake (stock character), a man habituated to immoral conduct
* Rake (theatre), the artificial slope of a theatre stage
Science and technology
* Rake receiver, a radio receiver
* Rake (geology), the angle between a feature on a ...
-like nature of its spiny frontal appendages.
Anatomy
File:20210518 Radiodonta frontal appendage Stanleycaris hirpex.png, alt=, Diagram of frontal appendage
File:Stanleycaris Turntable2 2.ogg, alt=, 3D reconstruction of frontal appendages
File:20210520 Stanleycaris hirpex oral cone.png, alt=, Oral cone
File:20210220 Stanleycaris size.png, alt=, Size estimation
''Stanleycaris'' was a small
radiodont
Radiodonta is an extinct Order (biology), order of stem-group arthropods that was successful worldwide during the Cambrian period. They may be referred to as radiodonts, radiodontans, radiodontids, anomalocarids, or anomalocaridids, although the ...
, with whole body specimen measured around , excluding the tail. Even based on the largest, -long isolated frontal appendage, the upper body length was thought to be less than long.
Unlike most
hurdiids with large head and broad neck region, the body of ''Stanleycaris'' was streamlined like those of
anomalocaridids
''Anomalocaris'' ("unlike other shrimp", or "abnormal shrimp") is an extinct genus of radiodont, an order of early-diverging stem-group arthropods. The first fossils of ''Anomalocaris'' were discovered in the ''Ogygopsis'' Shale of the Stephen F ...
and
amplectobeluids.
Head
The small head occupies about 15% of the total body length. Each lateral
compound eye
A compound eye is a visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidia, which are tiny independent photoreception units that consist of a cornea, lens, and photoreceptor cells which disti ...
was estimated to have around 1000
ommatidia
The compound eyes of arthropods like insects, crustaceans and millipedes are composed of units called ommatidia (singular: ommatidium). An ommatidium contains a cluster of photoreceptor cells surrounded by support cells and pigment cells. The ou ...
. In addition of a pair of
stalked
Stalking is unwanted and/or repeated surveillance by an individual or group toward another person. Stalking behaviors are interrelated to harassment and intimidation and may include following the victim in person or monitoring them. The term ...
lateral eyes, a third, large median eye was located behind its preocular sclerite (H-element). Similar structures were evident in the fossils of ''
Peytoia
''Peytoia'' is a genus of hurdiid radiodont that lived in the Cambrian period, containing two species, ''Peytoia nathorsti'' from the Miaolingian of Canada and ''Peytoia infercambriensis'' from Poland, dating to Cambrian Stage 3. Its two frontal ...
'' and ''
Lyrarapax
'' Lyrarapax'' is a radiodont genus of the family Amplectobeluidae that lived in the early Cambrian period 520 million years ago. Its neural tissue indicates that the radiodont frontal appendage is protocerebral, resolving parts of the arthropod ...
'', suggesting these genera possibly had a median eye too.
Contrary to the agreement around mid and late 2010s (based on the discovery of ''Lyrarapax'' since 2014) suggest radiodonts had only
protocerebrum
The protocerebrum is the first segment of the panarthropod brain.
Recent studies suggest that it comprises two regions.
Region associated with the expression of ''six3''
''six3'' is a transcription factor that marks the anteriormost part of ...
on their
cerebral ganglion
A ganglion is a group of neuron cell bodies in the peripheral nervous system. In the somatic nervous system this includes dorsal root ganglia and trigeminal ganglia among a few others. In the autonomic nervous system there are both sympatheti ...
, The
neuroanatomical
Neuroanatomy is the study of the structure and organization of the nervous system. In contrast to animals with radial symmetry, whose nervous system consists of a distributed network of cells, animals with bilateral symmetry have segregated, defi ...
evidence of ''Stanleycaris'' suggests radiodonts have both protocerebrum and
deutocerebrum
The supraesophageal ganglion (also "supraoesophageal ganglion", "arthropod brain" or "microbrain") is the first part of the arthropod, especially insect, central nervous system. It receives and processes information from the first, second, and th ...
, and circumesophageal connective that surround digestive system between them.
Unlike other radiodonts, the paired lateral sclerites (P-element) are not evident in any ''Stanleycaris'' specimens, suggesting they were exclusively absent in this genus.
Frontal appendage
The -long
frontal appendages are the most commonly found component of this genus. It comprise 14 segments (podomeres) with 5 long,
rake
Rake may refer to:
* Rake (stock character), a man habituated to immoral conduct
* Rake (theatre), the artificial slope of a theatre stage
Science and technology
* Rake receiver, a radio receiver
* Rake (geology), the angle between a feature on a ...
-like curved blades (endites) protruding from the ventral surface of podomere 3-7, while podomere 2 and 9 have short endites.
The upper surface bore a row of inner-facing, mostly forked robust spines (gnathites) which are unique to this genus.
Similar to ''
Peytoia
''Peytoia'' is a genus of hurdiid radiodont that lived in the Cambrian period, containing two species, ''Peytoia nathorsti'' from the Miaolingian of Canada and ''Peytoia infercambriensis'' from Poland, dating to Cambrian Stage 3. Its two frontal ...
'', the distal podomeres have claw-like dorsal and terminal spines.
Oral cone
The
mouth
In animal anatomy, the mouth, also known as the oral cavity, or in Latin cavum oris, is the opening through which many animals take in food and issue vocal sounds. It is also the cavity lying at the upper end of the alimentary canal, bounded on ...
was surrounded by a tetraradial
oral cone, which comprises 28 tooth plates instead of 32 like those of other
hurdiid
Hurdiidae is an extinct cosmopolitan family of radiodonts, a group of stem-group arthropods, which lived during the Paleozoic Era. It is the most long-lived radiodont clade, lasting from the Cambrian period to the Devonian period.
Descripti ...
genera.
Each of the 4 large plate have 2 additional nodes, and the mouth opening has no additional inner plates.
Trunk region
The trunk region have 17 segments with paired lateroventral flaps, as well as 4 caudal filiform blades on the tail. The setal blades (band of
gill
A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...
lamellae) were suggested to be positioned ventrally on each of the trunk segment,
contrary to the general reconstruction of radiodont with dorsal setal blades.
Paleoecology
''Stanleycaris'' was most likely a visual
predator
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...
that specialized primarily on macroscopic, soft-bodied benthic prey. Based on its
streamlined
Streamlines, streaklines and pathlines are field lines in a fluid flow.
They differ only when the flow changes with time, that is, when the flow is not steady.
Considering a velocity vector field in three-dimensional space in the framework of ...
body shape and broad trunk flaps, it may able to chase relatively fast-moving preys.
With strong differentiation of lateral–medial, inner–outer, and proximal–distal morphologies, ''Stanleycaris'' probably able to trap (by using endites), manipulate (by using distal raptorial portion), and masticate (by using gnathites) prey items.
Classification
''Stanleycaris'' was analysed to be one of the basalmost
hurdiid
Hurdiidae is an extinct cosmopolitan family of radiodonts, a group of stem-group arthropods, which lived during the Paleozoic Era. It is the most long-lived radiodont clade, lasting from the Cambrian period to the Devonian period.
Descripti ...
radiodont
Radiodonta is an extinct Order (biology), order of stem-group arthropods that was successful worldwide during the Cambrian period. They may be referred to as radiodonts, radiodontans, radiodontids, anomalocarids, or anomalocaridids, although the ...
, alongside ''
Peytoia
''Peytoia'' is a genus of hurdiid radiodont that lived in the Cambrian period, containing two species, ''Peytoia nathorsti'' from the Miaolingian of Canada and ''Peytoia infercambriensis'' from Poland, dating to Cambrian Stage 3. Its two frontal ...
'' and
''Schinderhannes'' which shares some anatomical similarities.
This suggests that the
anomalocaridid
Radiodonta is an extinct order of stem-group arthropods that was successful worldwide during the Cambrian period. They may be referred to as radiodonts, radiodontans, radiodontids, anomalocarids, or anomalocaridids, although the last two origi ...
/
amplectobeluid-like traits (e.g. streamlined body; small head sclerites; frontal appendages with curved dorsal spines) found in these hurdiids represent radiodont
ancestral characters.
File:Stanleycaris sp. KUMIP 153923.png, alt=, KUMIP 153923
The specimen KUMIP 153923 from the Cambrian
Wheeler Formation
The Wheeler Shale (named by Charles Walcott) is a Cambrian ( 507 Ma) fossil locality world-famous
for prolific agnostid and ''Elrathia kingii'' trilobite remains (even though many areas are barren of fossils)
and represents a Konzent ...
(
Utah
Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...
,
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
), which was described by Robison (1985) as a whole body of new
lobopodia
The lobopodians, members of the informal group Lobopodia (from the Greek language, Greek, meaning "blunt feet"), or the formally erected phylum Lobopoda Cavalier-Smith (1998), are panarthropods with stubby legs called lobopods, a term which may ...
n species ''
Aysheaia
''Aysheaia'' is an extinct genus of soft-bodied lobopod, known from the middle Cambrian of North America, with an average body length of 1–6 cm.
Anatomy
''Aysheaia'' has ten body segments, each of which has a pair of spiked, annulate le ...
prolata'', was reinterpreted as an isolated frontal appendage of ''Stanleycaris'' sp. by Pates, Daley & Ortega-Hernández (2017).
References
External links
*
Anomalocaridids
Articles containing video clips
Burgess Shale fossils
Fossil taxa described in 2010
Fossil taxa described in 2018
{{paleo-arthropod-stub