Carrolla

Carrolla is an extinct genus of brachystelechid 'microsaur' that lived in the Lower Permian in North America. It was named in 1986 by American paleontologists Wann Langston and Everett Olson. The type species, Carrolla craddocki, is the only known species.

Carrolla Temporal range: Lower Permian PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Amphibia
Subclass:	†Lepospondyli
Superorder:	†Microsauria
Family:	†Brachystelechidae
Genus:	†Carrolla
Species:	†C. craddocki
Binomial name
Carrolla craddocki

History of study

Carrolla was named for the type species by Langston & Olson (1986) for a single, complete skull collected from the early Permian of Archer County, Texas; the specimen is reposited at the Texas Memorial Museum in Austin.[1] They immediately recognized the similarity to 'Brachystelechus,' the eponymous genus from Europe; this genus was subsequently synonymized with Batropetes, traditionally considered a reptile but which had taxonomic precedent.[2] Numerous features were cited as evidence for an ability to burrow, which was considered rare among 'microsaurs' at the time, and several shared features with modern amphibians were noted, although some of these have been subsequently disproven. Maddin et al. (2011) provided a detailed re-description of the holotype based on CT data; this study was one of the first to explore 'microsaur' anatomy using tomographic methods.[3] These authors provided substantial new information on the internal anatomy, particularly the braincase, and recovered support for close affinities of brachystelechids and caecilians in the longstanding debate over the origin of modern amphibians. Mann et al. (2019) reported the first postcrania of the taxon based on a small block that was catalogued with the holotype skull but never described; the authors indicate that correspondence with K.W. Craddock, who found the holotype, corroborates that the postcrania block was recovered in association with the skull.[4] The authors also validated Glienke's (2015)[5] previous cursory interpretation of at least some of the teeth as tricuspid, a feature found in some other brachystelechids.

Anatomy

The most recent diagnosis was provided by Maddin et al. (2011)[3] and includes features such as a short, wide skull with a well-ossified anterior braincase. Some of the diagnostic features have been shown to be shared with other taxa following similar CT analyses of additional 'microsaurs'; more recent work on other brachystelechids including Glienke (2015)[5] and Pardo et al. (2015)[6] have provided additional features that separate those taxa from Carrolla. For example, both Quasicaecilia and Carrolla share extensively ossified posterior braincases and anterior braincases, but the morphology of some features, such as the element termed the 'presphenoid' by Pardo et al. differs between them. The presence of bicuspid teeth was reported by Langston & Olson, a feature of great interest because it has traditionally been considered to be a feature linking them to modern amphibians, the only living tetrapods with bicuspid teeth, but subsequent workers identified tricuspidity in the holotype.[4]

Relationships

Below is the strict consensus tree from Mann & Maddin (2019):[7]

Seymouria       Limnoscelis    Amniota    Petrolacosaurus     Captorhinus     Opisthodontosaurus       Ophiacodon     Dimetrodon      Recumbirostra    Pantylus     Llistrofus       Micraroter       Nannaroter     Pelodosotis             Huskerpeton     Cardiocephalus         Rhynchonkos       Aletrimyti     Dvellecanus               Brachydectes    Brachystelechidae    Quasicaecilia       Diabloroter       Batropetes     Carrolla

See also

• Prehistoric amphibian
• List of prehistoric amphibians

References

1. Langston Jr., Wann; Olson, E. C. (1986). "Carrolla craddocki: A New Genus and Species of Microsaur from the Lower Permian of Texas". Pearce-Sellards Series, Texas Memorial Museum, University of Texas at Austin. 43: 1–20. ISSN 0079-0354.
2. Carroll, Robert (1991-06-20). "Batropetes from the Lower Permian of Europe—a microsaur, not a reptile". Journal of Vertebrate Paleontology. 11 (2): 229–242. doi:10.1080/02724634.1991.10011390. ISSN 0272-4634.
3. Maddin, Hillary C.; Olori, Jennifer C.; Anderson, Jason S. (2011). "A redescription of Carrolla craddocki (Lepospondyli: Brachystelechidae) based on high-resolution CT, and the impacts of miniaturization and fossoriality on morphology". Journal of Morphology. 272 (6): 722–743. doi:10.1002/jmor.10946. ISSN 1097-4687. PMID 21484854.
4. Mann, Arjan; Olori, Jennifer C.; Maddin, Hillary C. (2018-11-02). "Postcranial anatomy of the 'microsaur' Carrolla craddocki from the Lower Permian of Texas". Journal of Vertebrate Paleontology. 38 (6): e1532436. doi:10.1080/02724634.2018.1532436. ISSN 0272-4634. S2CID 91617953.
5. Glienke, Sabine (2015-03-04). "Two new species of the genus Batropetes (Tetrapoda, Lepospondyli) from the Central European Rotliegend (basal Permian) in Germany". Journal of Vertebrate Paleontology. 35 (2): e918041. doi:10.1080/02724634.2014.918041. ISSN 0272-4634. S2CID 83855041.
6. Pardo, Jason D.; Szostakiwskyj, Matt; Anderson, Jason S. (2015-06-24). "Cranial Morphology of the Brachystelechid 'Microsaur' Quasicaecilia texana Carroll Provides New Insights into the Diversity and Evolution of Braincase Morphology in Recumbirostran 'Microsaurs'". PLOS ONE. 10 (6): e0130359. doi:10.1371/journal.pone.0130359. ISSN 1932-6203. PMC 4479878. PMID 26107260.
7. Mann, Arjan; Maddin, Hillary C. (2019-09-30). "Diabloroter bolti, a short-bodied recumbirostran 'microsaur' from the Francis Creek Shale, Mazon Creek, Illinois". Zoological Journal of the Linnean Society. 187 (2): 494–505. doi:10.1093/zoolinnean/zlz025. ISSN 0024-4082.