Lepidus praecisio

Lepidus praecisio
Temporal range: Upper Triassic,
Holotype ankle
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Genus: †Lepidus
Nesbitt & Ezcurra, 2015[1]
Species:
†L. praecisio
Binomial name
†Lepidus praecisio

Lepidus is a genus of extinct theropod from the Upper Triassic of the United States. It lived in the Otis Chalk localities of the Dockum Group in Texas, from 231 to 223 million years ago.[1][2]

Discovery

Hypothetical restoration

The locality from which Lepidus is known was discovered in the middle of February 1941 by the Works Progress Administration paleontology team in Texas. The precise geographic locality is unknown, but at the least it is known that the locality is eight miles southeast of the city of Big Spring in Howard County, Texas. Using Google Earth and USGS cartographic maps, the describing authors were able to deduce the fossils were located in the vicinity of Signal Peak. The locality is situated in the Colorado City Formation, which is constrained to about 231-223 Ma in the Carnian to Norian stages of the Upper Triassic.[2]

It was first described in 2015 by Nesbitt & Ezcurra, who decided it warranted a new taxon, which they named Lepidus praecisio. The generic name is Latin for "fascinating", and the specific name is Latin for "fragment", or "scrap". The holotype material includes a tibia, astragalus, and fibula. Other referred material includes a femur and maxilla. Nesbitt and Ezcurra stressed that the maxilla cannot be referred to Lepidus with any kind of confidence, but its morphology is most similar to neotheropods among all archosaurs known from the Colorado City Formation. The holotypic material is well-preserved and shows signs of muscle scars. The astragalus and calcaneum are clearly fused into one bone, with no visible suture. The tibia resembles that of neotheropods, in overall morphology. The shape of the tibia resembles the same in Camposaurus, Coelophysis, Tawa, Eodromaeus, and Herrerasaurus.[1]

Lepidus was one of eighteen dinosaur taxa from 2015 to be described in open access or free-to-read journals.[3]

Classification

Partial maxilla which may have belonged to the holotype

A phylogenetic analysis was conducted, including with and without referred material. The results are shown below:[1]

Neotheropoda

More recent phylogenetic analyses recovered this genus as a member or sister taxon of Neotheropoda outside Coelophysoidea.[4][5][6]

References

  1. 1 2 3 4 5 Nesbitt, Sterling J.; Ezcurra, Martin D. (13 July 2015). "The early fossil record of dinosaurs in North America: A new neotheropod from the base of the Upper Triassic Dockum Group of Texas" (PDF). Acta Palaeontologica Polonica. 60. doi:10.4202/app.00143.2014.
  2. 1 2 Lovelace, David M; Kufner, Aaron M; Fitch, Adam J; Curry Rogers, Kristina; Schmitz, Mark; Schwartz, Darin M; LeClair-Diaz, Amanda; St.Clair, Lynette; Mann, Joshua; Teran, Reba (2025-01-01). "Rethinking dinosaur origins: oldest known equatorial dinosaur-bearing assemblage (mid-late Carnian Popo Agie FM, Wyoming, USA)". Zoological Journal of the Linnean Society. 203 (1) zlae153. doi:10.1093/zoolinnean/zlae153. ISSN 0024-4082.
  3. ↑ "The Open Access Dinosaurs of 2015". PLOS Paleo.
  4. ↑ Marsh, Adam D.; Parker, William G.; Langer, Max C.; Nesbitt, Sterling J. (2019-05-04). "Redescription of the holotype specimen of Chindesaurus bryansmalli Long and Murry, 1995 (Dinosauria, Theropoda), from Petrified Forest National Park, Arizona" (PDF). Journal of Vertebrate Paleontology. 39 (3) e1645682. Bibcode:2019JVPal..39E5682M. doi:10.1080/02724634.2019.1645682. ISSN 0272-4634. S2CID 202865005. Archived (PDF) from the original on 2021-07-23. Retrieved 2020-06-09.
  5. ↑ Marsh, A.D.; Rowe, T.B. (2020). "A comprehensive anatomical and phylogenetic evaluation of Dilophosaurus wetherilli (Dinosauria, Theropoda) with descriptions of new specimens from the Kayenta Formation of northern Arizona". Journal of Paleontology. 94 (S78): 1–103. Bibcode:2020JPal...94S...1M. doi:10.1017/jpa.2020.14. S2CID 220601744.
  6. ↑ Spiekman SN, Ezcurra MD, Butler RJ, Fraser NC, Maidment SC (2021). "Pendraig milnerae, a new small-sized coelophysoid theropod from the Late Triassic of Wales". Royal Society Open Science. 8 (10) 210915. Bibcode:2021RSOS....810915S. doi:10.1098/rsos.210915. PMC 8493203. PMID 34754500.
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