''Pamelaria'' is an extinct
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
of
allokotosauria
Allokotosauria is a clade of early archosauromorph reptiles from the Middle to Late Triassic known from Asia, Africa, North America and Europe. Allokotosauria was first described and named when a new monophyletic grouping of specialized he ...
n
archosauromorph
Archosauromorpha ( Greek for "ruling lizard forms") is a clade of diapsid reptiles containing all reptiles more closely related to archosaurs (such as crocodilians and dinosaurs, including birds) rather than lepidosaurs (such as tuataras, l ...
reptile known from a single species, ''Pamelaria dolichotrachela'', from the
Middle Triassic
In the geologic timescale, the Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided in chronostratigraphy. The Middle Triassic spans the time between Ma and ...
of India.
''Pamelaria'' has sprawling legs, a long neck, and a pointed skull with nostrils positioned at the very tip of the snout. Among early archosauromorphs, ''Pamelaria'' is most similar to ''
Prolacerta
''Prolacerta'' is a genus of archosauromorph from the lower Triassic of South Africa and Antarctica. The only known species is ''Prolacerta broomi''. The generic name ''Prolacerta'' is derived from Latin meaning “before lizard” and its spec ...
'' from the
Early Triassic
The Early Triassic is the first of three epochs of the Triassic Period of the geologic timescale. It spans the time between Ma and Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic Series, which is a un ...
of South Africa and Antarctica. Both have been placed in the family
Prolacertidae. ''Pamelaria'', ''Prolacerta'', and various other
Permo-
Triassic
The Triassic ( ) is a geologic period and system (stratigraphy), system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Year#Abbreviations yr and ya, Mya), to the beginning of the Jurassic Period 201.36 ...
reptiles such as ''
Protorosaurus
''Protorosaurus'' ("first lizard") is a genus of lizard-like early reptiles. Members of the genus lived during the late Permian period in what is now Germany and Great Britain. Once believed to have been an ancestor to lizards, ''Protorosaurus'' ...
'' and ''
Tanystropheus
''Tanystropheus'' (Greek ~ 'long' + 'hinged') is an extinct archosauromorph reptile from the Middle and Late Triassic epochs. It is recognisable by its extremely elongated neck, which measured long—longer than its body and tail combined. T ...
'' have often been placed in a group of archosauromorphs called
Protorosauria
Protorosauria is an extinct polyphyletic group of archosauromorph reptiles from the latest Middle Permian ( Capitanian stage) to the end of the Late Triassic (Rhaetian stage) of Asia, Europe and North America. It was named by the English anatom ...
(alternatively called Prolacertiformes), which was regarded as one of the most
basal group of archosauromorphs. However, more recent
phylogenetic
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...
analyses indicate that ''Pamelaria'' and ''Prolacerta'' are more closely related to
Archosauriformes
Archosauriformes (Greek for 'ruling lizards', and Latin for 'form') is a clade of diapsid reptiles that developed from archosauromorph ancestors some time in the Latest Permian (roughly 252 million years ago). It was defined by Jacques Gauthier ...
than are ''Protorosaurus'', ''Tanystropheus'', and other protorosaurs, making Protorosauria a
polyphyletic
A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of conver ...
grouping.
A 2015 analysis by Nesbitt ''et al''. found that ''Pamelaria'' was the basalmost member of a newly formulated archosauromorph group also containing the
Trilophosauridae and the newly redescribed genus ''
Azendohsaurus
''Azendohsaurus'' is an extinct genus of herbivorous archosauromorph reptile from roughly the late Middle to early Late Triassic Period of Morocco and Madagascar. The type species, ''Azendohsaurus laaroussii'', was described and named by Jean- ...
'', which had previously been mistaken for a
sauropodomorph
Sauropodomorpha ( ; from Greek, meaning "lizard-footed forms") is an extinct clade of long-necked, herbivorous, saurischian dinosaurs that includes the sauropods and their ancestral relatives. Sauropods generally grew to very large sizes, had lon ...
dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
. This new group was called the Allokotosauria.
Later studies generally agreed with Nesbitt ''et al''.'s findings,
but some additionally postulated that ''Pamelaria'' was more closely related to ''Azendohsaurus'' than to trilophosaurids.
Description
![Pamelaria scale diagram](https://upload.wikimedia.org/wikipedia/commons/6/6c/Pamelaria_scale_diagram.png)
Based on known specimens, ''Pamelaria'' reached a length of about 2 m. The neck, made up of six thick and elongated
cervical vertebrae, comprises much of this length. The limbs are robust, roughly equal in size, and sprawl outward from the body. The
pectoral girdle
The shoulder girdle or pectoral girdle is the set of bones in the appendicular skeleton which connects to the arm on each side. In humans it consists of the clavicle and scapula; in those species with three bones in the shoulder, it consists of ...
is large and plate-like. The tail is thick near its base and narrows closer to its tip.
The skull of ''Pamelaria'' is small and pointed with small, conical teeth. The
naris
A nostril (or naris , plural ''nares'' ) is either of the two orifices of the nose. They enable the entry and exit of air and other gasses through the nasal cavities. In birds and mammals, they contain branched bones or cartilages called turbi ...
(the opening in the bone for the nasal passage) is a single hole positioned at the tip of the snout. The back margin of the skull viewed from above is strongly arched. The
orbits
In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as a p ...
or eye sockets are large. The upper
temporal fenestra
An infratemporal fenestra, also called the lateral temporal fenestra or simply temporal fenestra, is an opening in the skull behind the orbit in some animals. It is ventrally bordered by a zygomatic arch. An opening in front of the eye sockets ...
e at the top of the skull are small while the lower temporal fenestrae behind the orbits are quite large. Like those of protorosaurs, the skull of ''Pamelaria'' lacks a connection between the
quadrate and the
jugal
The jugal is a skull bone found in most reptiles, amphibians and birds. In mammals, the jugal is often called the malar or zygomatic. It is connected to the quadratojugal and maxilla, as well as other bones, which may vary by species.
Anatomy ...
bones along the bottom of the skull, meaning that each lower temporal fenestra is not fully enclosed by bone. The lower jaw has a large raised portion in front of the jaw joint called the
coronoid process.
Discovery and naming
Fossils of ''Pamelaria'' have been found in the Middle Triassic
Yerrapalli Formation
The Yerrapalli Formation is a Triassic rock formation consisting primarily of mudstones that outcrops in the Pranhita–Godavari Basin in southeastern India. The Yerrapalli Formation preserves fossils of freshwater and terrestrial vertebrates ...
in
Andhra Pradesh
Andhra Pradesh (, abbr. AP) is a state in the south-eastern coastal region of India. It is the seventh-largest state by area covering an area of and tenth-most populous state with 49,386,799 inhabitants. It is bordered by Telangana to the ...
, India. The known material represents six individuals from three fossil sites. The most well preserved is a mostly complete and articulated skeleton and is the
holotype
A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of sever ...
specimen of ''Pamelaria''. A second partial skeleton belongs to a smaller individual. The other individuals are represented by isolated bones found in association with bones of the archosaur ''
Yarasuchus
''Yarasuchus'' (meaning "red crocodile") is an extinct genus of avemetatarsalian archosaur that lived during the Anisian stage of the Middle Triassic of India.Bandyopadhyay, S. and Sengupta, D. P. (1999). Middle Triassic vertebrate faunas from ...
'', ''Pamelaria'' was named in 2003 in honor of vertebrate paleontologist
Pamela Lamplugh Robinson. The species name ''dolichotrachela'' means "long neck" in
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 ...
.
Classification
''Pamelaria'' is a
basal member of Archosauromorpha, the
clade or evolutionary grouping that includes crocodilians, birds, and all reptiles more closely related to crocodilians and birds than to lizards (which form their own clade,
Lepidosauromorpha
Lepidosauromorpha (in PhyloCode known as ''Pan-Lepidosauria'') is a group of reptiles comprising all diapsids closer to lizards than to archosaurs (which include crocodiles and birds). The only living sub-group is the Lepidosauria, which cont ...
). Among basal archosauromorphs, ''Pamelaria'' is most similar in appearance to ''
Prolacerta
''Prolacerta'' is a genus of archosauromorph from the lower Triassic of South Africa and Antarctica. The only known species is ''Prolacerta broomi''. The generic name ''Prolacerta'' is derived from Latin meaning “before lizard” and its spec ...
'' from the Early Triassic of South Africa and Antarctica. When ''Pamelaria'' was named in 2003, both were placed in the family Prolacertidae. ''Pamelaria'', ''Prolacerta'', and other prolacertids were considered to belong to a diverse group of archosauromorphs called Protorosauria, which also includes the families
Protorosauridae and
Tanystropheidae
Tanystropheidae is an extinct family of mostly marine archosauromorph reptiles that lived throughout the Triassic Period. They are characterized by their long, stiff necks formed from elongated cervical vertebrae with very long cervical ribs. So ...
. The features that are most often used to classify protorosaurs are long cervical vertebrae and a gap below the lower temporal fenestra of the skull, both of which are found in ''Pamelaria''.
Beginning in 1998,
phylogenetic
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...
analyses showed that ''Prolacerta'' was not closely related to other protorosaurs; it was found to be in a more
derived position than protorosaurs, closer the clade
Archosauriformes
Archosauriformes (Greek for 'ruling lizards', and Latin for 'form') is a clade of diapsid reptiles that developed from archosauromorph ancestors some time in the Latest Permian (roughly 252 million years ago). It was defined by Jacques Gauthier ...
. A 2009 analysis confirmed that this was also the case for ''Pamelaria''. Both ''Pamelaria'' and ''Prolacerta'' were closely related to Archosauriformes while other protorosaurs formed a clade near the base of Archosauromorpha. The 2009 analysis also found that Prolacertidae was
paraphyletic, with ''Prolacerta'' being more closely related to archosauriforms than is ''Pamelaria''. This result suggests that features such as a long neck that were once regarded as evidence of a close relationship between ''Pamelaria'' and ''Prolacerta'' instead evolved independently in both taxa. Below is the
cladogram
A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...
from the 2009 analysis showing the relationships of ''Pamelaria'' and other archosauromorphs:
Nesbitt ''et al.'' (2015) found ''Pamelaria'' to be the basalmost allokotosaurian.
Paleobiology
Posture
The neck of ''Pamelaria'' was probably held above the rest of the body in life. At the base of the neck, the
zygapophysial joints between successive vertebrae are angled to allow for dorsoventral or up-and-down movement of the neck. Closer to the skull the joints are angled in such a way that dorsoventral movement would be restricted but lateral or side-to-side movement would be possible. Therefore, ''Pamelaria'' would be able to raise and lower its neck from the base and turn its neck along the rest of its length. However, sideways movement would be limited because the cervical vertebrae are thick.
The tail of ''Pamelaria'' is thick and heavy, possibly acting as a counterbalance to the long neck. The tail is tall near its base due to high
neural arch
The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...
es above the vertebrae and long
chevrons
Chevron (often relating to V-shaped patterns) may refer to:
Science and technology
* Chevron (aerospace), sawtooth patterns on some jet engines
* Chevron (anatomy), a bone
* '' Eulithis testata'', a moth
* Chevron (geology), a fold in rock l ...
below them. Long
sacral
Sacral may refer to:
*Sacred
Sacred describes something that is dedicated or set apart for the service or worship of a deity; is considered worthy of spiritual respect or devotion; or inspires awe or reverence among believers. The property ...
and caudal ribs restricted lateral movement, making most of the tail inflexible. The shape of the
femur
The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates wit ...
(upper leg bone) indicates that ''Pamelaria'' had large
caudofemoralis muscles that further restricted the tail's movement (caudofemoralis muscles anchor to the base of the tail and insert into the femur).
The equal length of the fore and hindlimbs suggests that ''Pamelaria'' was quadrupedal. The limb bones join loosely with the pectoral and pelvic girdles. Their shape indicates that they sprawled outward in life, giving ''Pamelaria'' a posture similar to that of
lizards. ''Pamelaria'' would have rotated its limbs horizontally to move, pushing off from its outermost toe as do living lizards. To support its weight, ''Pamelaria ''may have used both its limbs and the base of its tail, possibly raising the rest of its tail while walking (a behavior also seen in some lizards) to reduce friction with the ground.
Diet
The small conical teeth that line the edges of the upper and lower jaws and the surface of the
palate
The palate () is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity.
A similar structure is found in crocodilians, but in most other tetrapods, the oral and nasal cavities are not truly separ ...
suggest that ''Pamelaria'' was insectivorous. Insect burrows are common in
Yerrapalli Formation
The Yerrapalli Formation is a Triassic rock formation consisting primarily of mudstones that outcrops in the Pranhita–Godavari Basin in southeastern India. The Yerrapalli Formation preserves fossils of freshwater and terrestrial vertebrates ...
, suggesting that insects would have been an abundant food source.
References
{{Taxonbar, from=Q15727711
Allokotosaurs
Prehistoric reptile genera
Middle Triassic reptiles of Asia
Triassic India
Fossils of India
Fossil taxa described in 2003