''Leiocephalus anonymous'', also known as the Atalaye giant curlytail lizard, is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

species of curly-tailed lizard discovered in cave deposits of northwestern

Haiti Haiti, officially the Republic of Haiti, is a country on the island of Hispaniola in the Caribbean Sea, east of Cuba and Jamaica, and south of the Bahamas. It occupies the western three-eighths of the island, which it shares with the Dominican ...

. The species is notable for its large size among curly-tailed lizards and its unique combination of ancestral and derived skeletal features. Its fossils remained unstudied for over 50 years before their formal description in 1984.

Taxonomy

Gregory Pregill published the

description Description is any type of communication that aims to make vivid a place, object, person, group, or other physical entity. It is one of four rhetorical modes (also known as ''modes of discourse''), along with exposition, argumentation, and narr ...

of this species in 1984, based on

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 preserve ...

specimens he found in

Smithsonian Institution The Smithsonian Institution ( ), or simply the Smithsonian, is a group of museums, Education center, education and Research institute, research centers, created by the Federal government of the United States, U.S. government "for the increase a ...

storage. The specimens, collected from cave deposits in northern

during the 1920s, had languished unstudied for over half a century. From a

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

perspective, research suggests that ''Leiocephalus anonymous'' exhibits a close evolutionary relationship with '' L. apertosulcus'' and '' L. cuneus'', collectively forming a

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

assemblage that shares a

common ancestor Common descent is a concept in evolutionary biology applicable when one species is the ancestor of two or more species later in time. According to modern evolutionary biology, all living beings could be descendants of a unique ancestor commonl ...

with '' L. greenwayi''.

Etymology

The specific epithet ''anonymous'' (from Greek, meaning "nameless") was chosen because the species remained unidentified for decades after its initial discovery.

Morphology

The fossils indicate an estimated snout-to-vent length (SVL) of for mature individuals, making ''Leiocephalus anonymous'' one of the larger members of its genus. Morphological comparisons suggest that ''L. anonymous'' may represent a reversal to a primitive character state due to the presence of a well-developed intramandibular septum. The species displayed distinctive skeletal features, particularly in its dentary bone structure. Its Meckelian groove exhibited an intermediate closure pattern, falling between the open configuration of ''L. apertosulcus'' and the fully fused state of other Leiocephalus species. The teeth showed a mix of simple and elaborate fleur-de-lis patterned tricuspid forms. Other key features included a pineal foramen wholly contained within the frontal bone and an exceptionally wide interorbital region.

Distribution

Fossil evidence comes exclusively from

cave Caves or caverns are natural voids under the Earth's Planetary surface, surface. Caves often form by the weathering of rock and often extend deep underground. Exogene caves are smaller openings that extend a relatively short distance undergrou ...

deposits near St. Michel de l'Atalaye in Haiti's Artibonite department. These rich deposits yielded diverse vertebrate remains, including mammals, birds, and other reptiles. Scientists believe the species' range likely encompassed much of northern

Hispaniola Hispaniola (, also ) is an island between Geography of Cuba, Cuba and Geography of Puerto Rico, Puerto Rico in the Greater Antilles of the Caribbean. Hispaniola is the most populous island in the West Indies, and the second-largest by List of C ...

Extinction

The extinction of ''Leiocephalus anonymous'' is attributed to environmental disturbances, possibly exacerbated by climatic changes at the end of the

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

and anthropogenic factors during early human colonization of the Antilles. The presence of rat (''

Rattus ''Rattus'' is a genus of muroid rodents, all typically called rats. However, the term rat can also be applied to rodent species outside of this genus. Species and description The best-known ''Rattus'' species are the black rat (''R. rattus'') ...

'') bones in the fossil deposits raises the possibility that ''L. anonymous'' persisted into post-Columbian times, although this remains uncertain due to potential contamination of sediment layers. The disappearance of ''L. anonymous'' reflects a broader extinction pattern in the

West Indies The West Indies is an island subregion of the Americas, surrounded by the Atlantic Ocean, North Atlantic Ocean and the Caribbean Sea, which comprises 13 independent island country, island countries and 19 dependent territory, dependencies in thr ...

, demonstrating how island species often prove especially vulnerable to environmental and human-driven changes.

References

{{Taxonbar, from=Q5120829 Leiocephalus Fossils of Haiti Fossil taxa described in 1984 Reptiles described in 1984