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| Cryptovaranoides microlanius Whiteside, Chambi-Trowell & Benton, 2022 Life restoration by L. Gandolfi. |
Abstract
Mammals, birds, and squamates (lizards, snakes, and relatives) are key living vertebrates, and thus understanding their evolution underpins important questions in biodiversity science. Whereas the origins of mammals and birds are relatively well understood, the roots of squamates have been obscure. Here, we report a modern-type lizard from the Late Triassic of England [202 million years (Ma)], comprising a partial skeleton, skull, and mandibles. It displays at least 15 unique squamate traits and further shares unidentatan and anguimorph apomorphies. The new discovery fixes the origin of crown Squamata as much older than had been thought, and the revised dating shows substantial diversification of modern-type squamates following the Carnian Pluvial Episode, 232 Ma ago.
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| Reconstructed skull and mandible of Cryptovaranoides microlanius, based mainly on the holotype PV R36822. Some key squamate features are labeled. Bones in light gray (nasal, parietal, and postfrontal) are unknown and speculatively reconstructed. Skull shown in lateral (A), ventral (D), and dorsal (E) views; right mandible in lateral (B), left mandible in medial (C) views. (F) Life restoration by L. Gandolfi. Estimated skull and mandible length is 14 mm for this juvenile specimen; isolated bones indicate that the skull can reach about 30 mm. Entire animal length ~ 25 cm. For more details of bones, see fig. S1. Outline drawings by S. Powell, University of Bristol. |
Infraclass DIAPSIDA Osborn, 1903
PAN-SQUAMATA sensu Gauthier and de Queiroz, 2020
SQUAMATA sensu de Queiroz and Gauthier, 2020
Cryptovaranoides gen. nov
Cryptovaranoides microlanius n. gen., n. sp.
Etymology— The genus name Cryptovaranoides is derived from the Greek word crypto, “hidden,” new Latin varan (from Arabic Waran meaning “dragon-lizard”), and the Greek suffix oides meaning “like.” The generic name is thus “hidden, lizard-like” (animal), referring to the fact that this fossil has remained unrecognized in a collection for nearly 70 years and that it was a small lizard-like animal (skull length maximum about 30 mm), living on karst limestone, perhaps hiding in the grykes (crevices). The species name microlanius derives from the Greek “micro” = small and Latin “lanius” meaning butcher. The recurved blade-like teeth demonstrate that the animal was a small efficient predator that could capture and immobilize prey quickly.
Holotype—NHMUK PV R36822, a partly articulated anterior skeleton and associated partial skull and lower jaws preserved on and in the red matrix of a small block of conglomeratic limestone. The left mandible and a partial skull (Fig. 1, A and B), including both maxillae and associated bones, are close to the articulated partial skeleton. ....
Locality and age—Triassic fissure deposit in Carboniferous Limestone, Cromhall Quarry, Tortworth, Gloucestershire, United Kingdom. Age is Rhaetian, probably late Rhaetian (equivalent of Cotham Member, Lilstock Formation), 201.6 to 201.8 Ma.
Diagnosis—Characterized by the following apomorphies: (i) maxillary and dentary with frequently replaced conical, pleurodont recurved teeth (Figs. 1, A to C, E, and F, 2, C and D, 3, A to G, and 4A) displaying labio-lingually compressed apices (upper part of the crown) and a prominent sharp carina on mesial and distal edges (Fig. 3, F and G). The mesial compressed region is somewhat more pronounced than the distal, and overall cross section of compressed region is oculiform-lanceolate. The mesial region of mid and posterior maxillary teeth develops a pronounced blade-like flange. ....
David I. Whiteside, Sofía A. V. Chambi-Trowell and Michael J. Benton. 2022. A Triassic Crown Squamate. SCIENCE ADVANCES. 8(48). DOI: 10.1126/sciadv.abq8274
Fossil discovery in storeroom cupboard shifts origin of modern lizard back 35 million years