''Lapillopsis'' 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 n ...

stereospondyl The Stereospondyli are a group of extinct temnospondyl amphibians that existed primarily during the Mesozoic period. They are known from all seven continents and were common components of many Triassic ecosystems, likely filling a similar ecolog ...

temnospondyl Temnospondyli (from Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') is a diverse order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carb ...

within the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Lapillopsidae Lapillopsidae is a family of Temnospondyli Temnospondyli (from Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') is a diverse order of small to giant tetrapods—often considered primitive amphibian ...

Fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s belonging to the genus have been found in the

Arcadia Formation The Arcadia Formation and its sub-unit, the Tampa Member, are Late Oligocene geologic formations in North Florida, United States. It is part of the Hawthorn Group. Age Period: Paleogene to Neogene Epoch: Early Late Oligocene through Pliocene F ...

(

Rewan Group Rewan is a given name. Notable people with the name include: * Rewan Amin (born 1996), Dutch footballer * Rewan Refaei (born 1996), Egyptian taekwondo practitioner See also * Rowan (name) * Rewan, Queensland, a rural locality in Queensland, Austr ...

) of

Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , established_ ...

, Australia.

History of study

The

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen( ...

and only known species is ''Lapillopsis nana,'' named in 1990 by Australian scientists Anne Warren and Mark Hutchinson. The name is derived from the Latin ''lapillus'' (pebble) and Greek -''opsis'' (appearance) in reference to the material of this species being collected from within small rocky nodules. There are two known specimens, both nearly complete skulls with associated mandibles and associated postcranial elements. An additional fourteen specimens from the same locality were described by Australian paleontologist Adam Yates in 1999.

Anatomy

''Lapillopsis'' was differentiated from the closely related ''

Rotaurisaurus ''Rotaurisaurus'' is an extinct genus of amphibian-grade tetrapod from the family Lapillopsidae. This genus is known only from an incomplete crushed skull and associated left jaw, together given the designation UTGD (University of Tasmania Geolog ...

'' from Australia by several features: (1) a deep, semi-elliptical otic notch; (2) an abbreviated posterior skull table; (3) a broad shallow sulcus extending from the posterolateral corner of the quadratojugal to the posterior orbital margin; (4) a broadly flared anterior end of the cultriform process; (5) pterygoid-palatine separation, resulting in an ectopterygoid framing the interpterygoid vacuity; (6) jugal terminating at anterior orbital margin. The skull and mandible are particularly well-known, permitting a more or less complete reconstruction. Postcranial material consists largely of the pectoral and forelimb regions and a few vertebrae.

Phylogenetic relationships

When it was named, ''Lapillopsis'' was identified as a micropholid

dissorophoid Dissorophoideans are a clade of medium-sized, temnospondyl amphibians that appeared during the Moscovian in Euramerica, and continued through to the Late Permian and the Early Triassic of Gondwana. They are distinguished by various details of t ...

; dissorophoids are almost exclusively

Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...

in occurrence with the exception of ''

Micropholis ''Micropholis'' is group of trees in the family Sapotaceae, described as a genus in 1891. (2001): World Checklist of Sapotaceae &ndash''Micropholis'' The Board of Trustees of the Royal Botanic Gardens, Kew. Retrieved 2008-DEC-24. These trees a ...

'' from the

Early Triassic The Early Triassic is the first of three epochs of the Triassic Period of the geologic timescale. It spans the time between Ma and Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic Series, which is a ...

Karoo Basin The Karoo Supergroup is the most widespread stratigraphic unit in Africa south of the Kalahari Desert. The supergroup consists of a sequence of units, mostly of nonmarine origin, deposited between the Late Carboniferous and Early Jurassic, a perio ...

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring count ...

. Because computer-assisted phylogenetics were not widely available at the time, the authors made comparisons of distinctive features with those known in other clades and found many similarities with dissorophoids. At the time, dissorophoid systematics remained partially in flux, particularly as it related to several small-bodied terrestrial forms, and Warren and Hutchinson revived Micropholidae, originally created by Watson (1919), to encompass both ''Micropholis'' and ''Lapillopsis,'' while noting that the latter lacked several apomorphies of Dissorophoidea. Yates' (1999) description of additional material of ''Lapillopsis'' and the new taxon ''Rotaurisaurus'' led him to create the family Lapillopsidae for this unusual group of small-bodied stereospondyls. Yates' phylogenetic analysis, as well as that of Yates & Warren (2000), recovered lapillopsids at the base of Stereospondyli. A supertree analysis by Ruta et al. (2003) recovered them in a vastly different position, as the sister group to eryopoids, dissorophoids (inclusive of modern amphibians), and zatracheidids. ''Lapillopsis'' was found as the sister to ''Rotaurisaurus'' in a 1999 analysis that found the

as basal stereospondyls.Yates, A. M. 1999. The Lapillopsidae: a new family of small temnospondyls from the Early Triassic of Australia. Journal of Vertebrate Paleontology 19: 302-320. https://doi.org/10.1080/02724634.1999.10011143 The most recent analysis of stereospondylomorphs by Eltink et al. (2019) recovered ''Lapillopsis'' within

Lydekkerinidae Lydekkerinidae is a family of stereospondyl temnospondyls that lived in the Early Triassic period. During this time period, lydekkerinids were widely distributed, with putative remains reported from Russia, Greenland, India, South Africa, Madaga ...

, another small-bodied Early Triassic group, as the sister taxon of ''

Lydekkerina ''Lydekkerina'' is an extinct genus of stereospondyl temnospondyl. It is the type genus of the family Lydekkerinidae. Fossils have been collected from Early Triassic deposits in South Africa and Australia. The type species is ''L. huxleyi'', fi ...

,'' somewhat similar to the results of McHugh's 2012 dissertation. This is in contradiction to previous studies in which ''Lapillopsis'' has been recovered: outside of Lydekkerinidae but as its sister group, with dissorophoids, as the sister taxon of short-snouted stereospondyl clades like lydekkerinids and metoposaurids, or closely related to brachyopoids. There is a general consensus that lapillopsids are at least stereospondylomorphs if not stereospondyls proper, but there is no clear agreement beyond that. Previous workers have highlighted the potential that specimens may not represent adults or that diminished body size may cause attraction with other small-bodied taxa, like lydekkerinids, in an analysis.

References

{{Taxonbar, from=Q15051787 Stereospondyls Triassic temnospondyls of Australia Prehistoric amphibians of Australia Fossil taxa described in 1990