''Leptopleuron'' 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 ...

procolophonid Procolophonidae is an extinct family of small, lizard-like parareptiles known from the Late Permian to Late Triassic that were distributed across Pangaea, having been reported from Europe, North America, China, South Africa, South America, Antarc ...

that lived in the dry lands during the

late Triassic The Late Triassic is the third and final epoch of the Triassic Period in the geologic time scale, spanning the time between Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch and followed by the Early Jurassic Epoch. ...

in Elgin of northern

Scotland Scotland (, ) is a Countries of the United Kingdom, country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a Anglo-Scottish border, border with England to the southeast ...

and was the first to be included in the clade of Procolophonidae. First described by English

paleontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...

and

biologist A biologist is a scientist who conducts research in biology. Biologists are interested in studying life on Earth, whether it is an individual Cell (biology), cell, a multicellular organism, or a Community (ecology), community of Biological inter ...

Sir Richard Owen Sir Richard Owen (20 July 1804 – 18 December 1892) was an English biologist, comparative anatomist and paleontologist. Owen is generally considered to have been an outstanding naturalist with a remarkable gift for interpreting fossils. Ow ...

, ''Leptopleuron'' is derived from two Greek bases, ''leptos'' for "slender" and ''pleuron'' for "rib," describing it as having slender ribs. The fossil is also known by a second name, ''Telerpeton'', which is derived from the Greek bases ''tele'' for "far off" and ''herpeton'' for "reptile." In Scotland, ''Leptopleuron'' was found specifically in the

Lossiemouth Sandstone The Lossiemouth Sandstone is a Middle to Late Triassic (Ladinian to Norian) age geological formation. It is exposed on the south side of the Moray Firth near Lossiemouth and near Golspie in Sutherland. Dinosaur remains are among the fossils th ...

Formation. The yellow sandstone it was located in was poorly lithified with wind coming from the southwest. The environment is also described to consist of

barchan A barchan or barkhan dune (from Kazakh бархан ) is a crescent-shaped dune. The term was introduced in 1881 by Russian naturalist Alexander von Middendorf, based on their occurrence in Turkestan and other inland desert regions. Barchans ...

dunes A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, fl ...

due to the winds, ranging up to 20 m tall that spread during dry phases into flood plains. Procolophonoids such as ''Leptopleuron'' were considered an essential addition to the terrestrial ecosystem during the

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 ...

Discovery and history

Discovered near Elgin, northern Scotland, from the Lossiemouth Formation in 1851, the fossil was examined and named ''Leptopleuron'' by Richard Owen. The reptilian fossil was initially evidence against progressionism, supporting the words of Charles Lyell, but with discussion was later accepted from the Triassic and for progressionism in 1860 after he became a progressionist. Controversy arose later when news broke out that the discoverer asked English paleontologist

Gideon Mantell Gideon Algernon Mantell MRCS FRS (3 February 1790 – 10 November 1852) was a British obstetrician, geologist and palaeontologist. His attempts to reconstruct the structure and life of ''Iguanodon'' began the scientific study of dinosaurs: in ...

to make a lengthier description of the fossil, calling it ''Telerpeton''. The general consensus that Owen produced a description of the fossil with hostility toward both Lyell and Mantell was also an issue. However, later analysis found that Mantell only produced a description as requested by Lyell, knowing that Owen was composing his own at the same time. ''Leptopleuron'' is the most accepted term for the reptile as Owen published before Mantell and made the most accurate interpretations.

Description

''Leptopleuron'' was a small, lizard-like animal of 270 mm that possessed a long tail as well as gastralia in contrast to '' Sclerosaurus'', and a slight triangular depression on its

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 ...

. As a reptile, five metatarsals were observed with lengths of roughly 8 mm with unknown values for some. In terms of its dentary, towards the posterior end, the ramus is notably deep. Its sacral ribs do not attach to the vertebrae after reconstruction of the fossil. The neural spines of ''Leptopleuron'', in particular, lean backwards as comparable and observed in '' Anomoiodon liliensterni'' and the genus '' Kapes''.

Acrodont Acrodonty (from Greek ''akros'' 'highest' + ''dont'' 'tooth') is an anatomical placement of the teeth at the summit of the alveolar ridge of the jaw, without sockets, characteristic of bony fish. Functionally, acrodont tooth implantation may be rela ...

dentition is evident in leptopleurons as well. A head illustration of Leptopleuron

Osteology of the skull

After reconstruction, the skull reached 55 mm long. The width of the skull was as long as the length of the skull when ignoring the quadratojugal horns as well. Some features of ''Leptopleuron'' include the size of its frontals. In contrast to other taxa, the width in the middle of the orbits are not the same as the width of its frontals in the anterior segment. ''Leptopleuron'' demonstrates a narrower anterior portion instead. No septomaxilla was observed, but the external naris is oval and immense in size. The maxilla contained five teeth with a significant difference for the tooth row as in contrast to ''

Hypsognathus ''Hypsognathus'' (from el, ῠ̔́ψος , 'height' and el, γνάθος , 'jaw') is an extinct genus of procolophonid parareptile from the Late Triassic of New Jersey, Connecticut, and Nova Scotia.Sues, H.-D.,Olsen, P.E., Scott,D.M, and Spe ...

'', the tooth row ended around the anterior region of the orbitotemporal opening. The prefrontal of ''Leptopleuron'' is seen to have dorsal exposure in the center of the lacrimal and frontal bones with the anterior edge enveloped by the nasals. The lacrimal is extremely concave at the whole orbital region, creating an immense depression heading toward the snout interior. This depression is known to enter the posterior of the orbitonasal canal after analysis. The parietal occupies the space for the postfrontal as this feature is absent in ''Leptopleuron''. The pineal foramen is large and between the parietals and frontals. Its orbitotemporal openings are not relatively long and are similar to those of ''Procolophon''. The jugal is also known to come into contact with the posterolateral extension of the nasal at its anterior end and barely touches the postorbital. The two spines of the quadratojugal are both flattened dorsoventrally, contain evident grooves, and are roughly the same size. ''Leptopleuron'' does not have a quadrate foramen as well, but the center part of the quadrate is stretched transversely. Notably, this bone is seen to connect with the pterygoid at the quadrate flange. ''Leptopleuron'' has also been identified to have vomerine dentition with short and long pairs of fangs. The tail fangs are at the anterior end of the vomer while the posterior end holds the short fangs. The palatine can only be seen in dorsal view and not in palatal view.

The braincase

Sharing similarities with other procolophonids, the braincase of ''Leptopleuron'' consists of a relatively long basisphenoid that covers the front part of the basioccipital. Other apomorphies include a tripartite occipital

condyle A condyle (;Entry "condyle"
in
foramen magnum as it is integrated with the prootic located anterolaterally. On the supraoccipital, a slight groove can be seen at each anteroventral extremity, particularly at the dorsolateral side. ''Leptopleuron'' is also characterized by its opisthotic having no foramen on the ventral ramus, specifically for nerve IX. The opisthotic is identified by a short transverse ridge that flanks a relatively deep and crescent moon-like notch ventrally. As for the prootic, the anteroventral process extends out into a free-standing distal plate rounded at the anterior. Characteristic of ''Leptopleuron'' as well is its extremely tiny stapes with a cone-like and obtusely sub-triangular footplate in lateral view. It was also known that its opisthotic and basioccipital did not come into contact with each other.

Paleobiology

Diet

Based on its dentition, ''Leptopleuron'' likely fed on coarse and fibrous vegetation or hard-shelled invertebrates as it possessed two-cusped marginal teeth that were labio-lingually spread out. Analysis also suggests vegetation in its diet as a procolophonid because of its trunks being larger and wider than those belonging to ''

Owenettidae Owenettidae is an extinct family of procolophonian parareptiles. Fossils have been found primarily from Africa and Madagascar, with one genus present from South America. It is the sister taxon to the family Procolophonidae. The family was const ...

'', indicated by their slimmer body shape.

Burrowing

The horned triangular head of ''Leptopleuron'', as well as an overbite comparable to the horned sand lizard, were evident of its burrowing lifestyle. With an overbite aiding in less ingestion of dirt, along with spade-like

unguals An ungual (from Latin ''unguis'', i.e. ''nail'') is a highly modified distal toe bone which ends in a hoof, claw, or nail. Elephants and ungulates have ungual phalanges, as did the sauropods and horned dinosaurs. A claw is a highly modified ungual ...

and strong limbs for efficient digging, ''Leptopleuron'' was likened to today's burrowers of ''

Phrynosoma Horned lizards (''Phrynosoma''), also known as horny toads or horntoads, are a genus of North American lizards and the type genus of the family Phrynosomatidae. The common names refer directly to their horns or to their flattened, rounded bodies, ...

'', a genus consisting of horned lizards. Skepticism remains, however, due to both its manus and pes having slender phalanges and unguals compared to ''

Procolophon ''Procolophon'' is a genus of lizard-like procolophonid parareptiles that first appeared in the Early Triassic (Induan) of South Africa, Brazil, and Antarctica. It persisted through the Permian–Triassic extinction event, but went extinct in ...

'', which is characteristically inefficient for dredging through dirt.

References

{{Taxonbar, from=Q6528277 Fossils of Scotland Late Triassic reptiles of Europe Leptopleuronines Triassic Scotland 1851 in Scotland Prehistoric reptile genera