# Rileymillerus

> Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Rileymillerus
> Markdown URL: https://mediated.wiki/source/Rileymillerus.md
> Source: https://en.wikipedia.org/wiki/Rileymillerus
> Source revision: 1053398748
> License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/)

Extinct genus of amphibians

Rileymillerus Temporal range: Late Triassic, 223–200 Ma PreꞒ Ꞓ O S D C P T J K Pg N Scientific classification Kingdom: Animalia Phylum: Chordata Clade: Tetrapoda Order: †Temnospondyli Suborder: †Stereospondyli Superfamily: †Metoposauroidea Genus: †Rileymillerus Bolt and Chatterjee, 2000 Type species †Rileymillerus cosgriffi Bolt and Chatterjee, 2000

***Rileymillerus*** is an extinct [genus](/source/Genus) of [temnospondyl](/source/Temnospondyl) amphibian from the [Late Triassic](/source/Late_Triassic) Post Quarry in the [Dockum Group](/source/Dockum_Group) of Texas that was described by John Bolt and Sankar Chatterjee in 2000.[1] The [holotype](/source/Holotype), a nearly complete skull with articulated jaws, is housed at the [Museum of Texas Tech University](/source/Museum_of_Texas_Tech_University). The genus is named for Riley Miller, who allowed Chatterjee to work on the Post Quarry, and the species is named for the paleontologist John Cosgriff.

## Description

*Rileymillerus cosgriffi* most closely resembles the poorly-known *Latiscopus disjunctus* that was described from similarly aged deposits of the Dockum Group near Otis Chalk, Texas.[2] As was noted by Wilson (1948) and Bolt & Chatterjee (2000), both of these taxa differ substantially from the morphology seen in large, flat-skulled aquatic temnospondyls of the Late Triassic ([metoposaurids](/source/Metoposauridae) in North America). Examples of their more unusual anatomy (most of which are confidently known only in *R. cosgriffi*) include the absence of a lacrimal bone, the presence of a lateral exposure of the palatine bone, a tall skull with laterally facing orbits, and an anteromedial inflection of the palatal ramus of the pterygoid. Both are also exceptionally small for Triassic temnospondyls, with skull lengths estimated around 3.5 cm (compared to those of metoposaurids, which exceeded 50 cm), and appear to have been relatively terrestrial (evidenced by an absence of lateral line grooves found in aquatic temnospondyls). Other than the holotype skull, only a few small, isolated, potentially diplospondylous intercentra were referred to *R. cosgriffi.*

## Classification

The phylogenetic relationships of *Rileymillerus* have historically been unresolved. Bolt & Chatterjee (2000) immediately recognized the similarities with *Latiscopus,* which was placed in a monogeneric family, the [Latiscopidae](/source/Latiscopidae), but which remains poorly-resolved (and considered as a *nomen dubium* by Bolt & Chatterjee).[1] Affinities with the similarly enigmatic *[Almasaurus habbazi](/source/Almasaurus)* from the Late Triassic of Morocco were considered but ultimately considered to be largely superficial similarities related to their shared small size; various other differences between the taxa exist. Bolt & Chatterjee considered close affinities with [brachyopoids](/source/Brachyopoidea) to be the most probable at the time, but they did not conclusively place *Rileymillerus* within the clade and did not perform a phylogenetic analysis to test this hypothesis, thus designating it as Temnospondyli [incertae sedis](/source/Incertae_sedis). Subsequent analysis of *Rileymillerus* within a phylogenetic analysis recovered it as being close to both *Almasaurus* and to [metoposaurids](/source/Metoposaurid) (see below).[3] This interpretation has been predicated on the interpretation of the small bone at the anteroventral margin of the orbit. Bolt & Chatterjee (2000) identified it as a lateral exposure of the palatine, a feature typically seen in Paleozoic and not Mesozoic temnospondyls, which resulted in the interpretation of an absent lacrimal, a rare condition best seen in rhytidosteids and brachyopoids. Conversely, Schoch (2008) interpreted this bone as a lacrimal in a restricted position similar to that of *Almasaurus* and metoposaurids.[3] Most recently, *Rileymillerus* has been shown to be closely related to brachyopoids and plagiosauroids and to *[Chinlestegophis jenkinsi](/source/Chinlestegophis)*, a similarly small Late Triassic temnospondyl interpreted as a stem caecilian.[4]

## Phylogeny

Below is a [cladogram](/source/Cladogram) from Schoch (2008):

Stereospondyli Rhinesuchidae Lydekkerina Rhytidosteidae Brachyopoidea Siderops Batrachosuchus Laidleria Plagiosauroidea Gerrothorax Plagiosaurus Capitosauroidea Trematosauria Aphaneramma Trematolestes Lyrocephaliscus Rileymillerus Almasaurus Callistomordax Metoposauridae

The results of the phylogenetic analysis of Pardo et al. (2017):

Stereospondyli Rhinesuchidae Lydekkerina Capitosauria Trematosauria Metoposauroidea Chigutisauridae Brachyopoidea Plagiosauroidea Rileymillerus Chinlestegophis caecilians

## References

1. ^ [***a***](#cite_ref-BC00_1-0) [***b***](#cite_ref-BC00_1-1) Bolt, John R.; Chatterjee, Sankar (2000). "A New Temnospondyl Amphibian from the Late Triassic of Texas". *Journal of Paleontology*. **74** (4): 670. [doi](/source/Doi_(identifier)):[10.1666/0022-3360(2000)074<0670:ANTAFT>2.0.CO;2](https://doi.org/10.1666%2F0022-3360%282000%29074%3C0670%3AANTAFT%3E2.0.CO%3B2).

1. **[^](#cite_ref-2)** Wilson, John A. (1948). "A Small Amphibian from the Triassic of Howard County". *Journal of Paleontology*. **22** (3): 359–361. [JSTOR](/source/JSTOR_(identifier)) [1299405](https://www.jstor.org/stable/1299405).

1. ^ [***a***](#cite_ref-SRR08_3-0) [***b***](#cite_ref-SRR08_3-1) Schoch, R. R. (2008). ["A new stereospondyl from the German Middle Triassic, and the origin of the Metoposauridae"](https://doi.org/10.1111%2Fj.1096-3642.2007.00363.x). *Zoological Journal of the Linnean Society*. **152**: 79–113. [doi](/source/Doi_(identifier)):[10.1111/j.1096-3642.2007.00363.x](https://doi.org/10.1111%2Fj.1096-3642.2007.00363.x).

1. **[^](#cite_ref-4)** Pardo, Jason D.; Small, Bryan J.; Huttenlocker, Adam K. (2017). ["Stem caecilian from the Triassic of Colorado sheds light on the origins of Lissamphibia"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5502650). *Proceedings of the National Academy of Sciences of the United States of America*. **114** (27): E5389–E5395. [doi](/source/Doi_(identifier)):[10.1073/pnas.1706752114](https://doi.org/10.1073%2Fpnas.1706752114). [ISSN](/source/ISSN_(identifier)) [1091-6490](https://search.worldcat.org/issn/1091-6490). [PMC](/source/PMC_(identifier)) [5502650](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5502650). [PMID](/source/PMID_(identifier)) [28630337](https://pubmed.ncbi.nlm.nih.gov/28630337).

- [Paleontology portal](https://en.wikipedia.org/wiki/Portal:Paleontology)

v t e Stereospondyli Kingdom: Animalia Phylum: Chordata Clade: Tetrapodomorpha Order: Temnospondyli Tetrapodomorpha see Tetrapodomorpha Temnospondyli see Temnospondyli Stereospondyli see below↓ Stereospondyli Stereospondyli Arachana Capulomala Peltobatrachus Lapillopsidae Lapillopsis Manubrantlia Rhigerpeton Rotaurisaurus Rhinesuchidae Australerpeton? Broomistega Laccosaurus Parapytanga? Rastosuchus Rhineceps Rhinesuchoides Rhinesuchus Uranocentrodon Lydekkerinidae Chomatobatrachus Cryobatrachus Deltacephalus Eolydekkerina Indobenthosuchus Luzocephalus? Lydekkerina Capitosauria Antarctosuchus Bukobaja Calmasuchus Capitosaurus Cherninia Cyclotosaurus Edingerella Eocyclotosaurus Eryosuchus Heptasaurus Huangfuchuansuchus Jammerbergia Kestrosaurus Kupferzellia Mastodonsaurus Meyerosuchus Odenwaldia Paracyclotosaurus Parotosuchus Quasicyclotosaurus Procyclotosaurus Promastodonsaurus Rhadalognathus Samarabatrachus Sassenisaurus Sclerothorax Selenocara Stanocephalosaurus Stenotosaurus Subcyclotosaurus Tatrasuchus Vladlenosaurus Volgasaurus Volgasuchus Warrenisuchus Watsonisuchus Wellesaurus Wetlugasaurus Xenotosuchus Yuanansuchus Trematosauria see below↓ Trematosauria Trematosauria Almasaurus Bothriceps Callistomordax Chinlestegophis Keratobrachyops Laidleria Latiscopus Qantas Rileymillerus Syrtosuchus Uruyiella Benthosuchidae Benthosuchus Kwatisuchus Trematosauridae Angusaurus Aphaneramma Cosgriffius Erythrobatrachus Gonioglyptus Hyperokynodon Icanosaurus Indolyrocephalus Inflectosaurus Lyrocephaliscus Microposaurus Panchetosaurus Platystega Prothoosuchus Stoschiosaurus Tertrema Tertremoides Thoosuchus Tirraturhinus Trematolestes Trematosuchoides Trematosaurus Trematosuchus Trematotegmen Wantzosaurus Metoposauridae Anaschisma Apachesaurus Arganasaurus Buettnererpeton Dutuitosaurus Metoposaurus Panthasaurus Rhytidosteidae Boreopelta Mahavisaurus Nanolania Peltostega Pneumatostega Rhytidosteus Sangaia Trucheosaurus Derwentiinae Arcadia Acerastia Deltasaurus Derwentia Indobrachyops Rewana Chigutisauridae Arenaerpeton Chigutisaurus Compsocerops Koolasuchus Pelorocephalus Siderops Brachyopidae Banksiops Bathignathus Batrachosaurus Batrachosuchoides Batrachosuchus Blinasaurus Brachyops Gobiops Hadrokkosaurus Notobrachyops Platycepsion Sinobrachyops Vanastega Vigilius Xenobrachyops Plagiosauridae Gerrothorax Megalophthalma Plagiobatrachus Plagiorophus Plagiosaurus Plagioscutum Plagiosternum Plagiosuchus See also: Trematosauroidea Metoposauroidea Rhytidosteoidea Brachyopomorpha Brachyopoidea Plagiosauroidea Category

Taxon identifiers Rileymillerus Wikidata: Q7334270 GBIF: 4815845 IRMNG: 1249698 Open Tree of Life: 3621029 Paleobiology Database: 144437

---
Adapted from the Wikipedia article [Rileymillerus](https://en.wikipedia.org/wiki/Rileymillerus) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Rileymillerus?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.