''Voay'' 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 nom ...

of crocodile from

Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...

that lived during the Late Pleistocene to

Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togeth ...

, containing only one species, ''V. robustus''. Numerous subfossils have been found, including complete skulls, noted for their distinctive pair of horns on the posterior, as well as vertebrae and

osteoderm Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinc ...

s from such places as Ambolisatra and Antsirabe. The genus is thought to have become extinct relatively recently. It has been suggested to have disappeared in the extinction event that wiped out much of the endemic megafauna on Madagascar, such as the

elephant bird Elephant birds are members of the extinct ratite family Aepyornithidae, made up of flightless birds that once lived on the island of Madagascar. They are thought to have become extinct around 1000-1200 CE, probably as a result of human activity. ...

and Malagasy hippo, following the arrival of humans to Madagascar around 2000 years ago. Its name comes from the Malagasy word for crocodile.

Description

One unusual feature of ''V. robustus'' that distinguishes it from other crocodilians is the presence of prominent "horns" extending from the posterior portion of the skull. They are actually the posterolaterally extended corners of the

squamosal bone The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone. In most tetrapods, the squamosal and quadratojugal bones form the cheek series of the skull. The bone forms an ancestral c ...

. Other related crocodilians such as ''

Aldabrachampsus ''Aldabrachampsus'' is an extinct genus of small horned crocodile known from fragmentary remains. It lived during the Pleistocene on Aldabra Atoll, Seychelles in the western Indian Ocean. The name ''Aldabrachampsus dilophus'' means "Two-crested ...

'' also had similar bony projections, although in ''Aldabrachampsus'' these projections were more like crests than horns. Another diagnostic characteristic is the near-exclusion of the

nasals In phonetics, a nasal, also called a nasal occlusive or nasal stop in contrast with an oral stop or nasalized consonant, is an occlusive consonant produced with a lowered velum, allowing air to escape freely through the nose. The vast majorit ...

from the external naris. It had a shorter and deeper snout than the extant ''Crocodylus niloticus'', as well as relatively robust limbs. The osteoderms had tall keels and were dorsally symmetrical with curved lateral margins, running the entire length of the postcranial body. ''V. robustus'' has been estimated to have obtained lengths up to 5 m (16.4 ft) and a weight of 170 kg (375 lbs). These estimates suggest that ''V. robustus'' was the largest predator to have existed in Madagascar in recent times. Its size, stature, and presumed behavior is similar to the modern

Nile crocodile The Nile crocodile (''Crocodylus niloticus'') is a large crocodilian native to freshwater habitats in Africa, where it is present in 26 countries. It is widely distributed throughout sub-Saharan Africa, occurring mostly in the central, eastern, ...

(''Crocodylus niloticus''). Because ''V. robustus'' shared so many similarities with the Nile crocodile there must have been a great deal of interspecific competition for resources between the two crocodile genera if they were to have coexisted with one another. It has recently been proposed that the Nile crocodile only migrated to the island from mainland

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

after ''V. robustus'' had become extinct in Madagascar. However, this was subsequently disproved after some '' Crocodylus'' specimens from Madagascar were found to be over 7,000 years old and contemporaneous with ''Voay''.

Phylogenetics

When ''V. robustus'' was first described in 1872, it was originally assigned to the genus '' Crocodylus''. It was later found to morphologically have had more in common with the extant ''Osteolaemus'', or dwarf crocodile, than ''Crocodylus''. Some features it shared with ''Osteolaemus'' include a depressed pterygoid surface that forms a

choana The choanae (singular choana), posterior nasal apertures or internal nostrils are two openings found at the back of the nasal passage between the nasal cavity and the throat in tetrapods, including humans and other mammals (as well as crocodilia ...

l "neck" on the palate. Because it was not close enough to be placed in the same genus as the dwarf crocodile, it was assigned to the new genus in 2007. Before this reassignment, the species was considered by some to be synonymous with ''Crocodylus niloticus''. However, this was most likely due to a misinterpretation of remains from the living ''C. niloticus'' with ''V. robustus'' and the poor description of the original material from which the species was described.Brochu, C. A. and Storrs, G. W. (1995). The giant dwarf crocodile: a reappraisal of ''‘Crocodylus’ robustus'' from the Quaternary of Madagascar. ''In:'' Patterson, Goodman, and Sedlock, eds., ''Environmental Change in Madagascar''. p. 70. In contrast to the morphological similarities with ''Osteolaemus'', a 2021 study using

paleogenomics Paleogenomics is a field of science based on the reconstruction and analysis of genomic information in extinct species. Improved methods for the extraction of ancient DNA (aDNA) from museum artifacts, ice cores, archeological or paleontological site ...

found ''Voay'' to be a sister group to ''Crocodylus'', with both genera diverging in the mid-late Oligocene; this indicates that the apparent similarities with ''Osteolaemus'' are likely due to

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...

. The below

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...

shows the results of the latest study:

References

{{Taxonbar, from=Q22113584, from2=Q1284680 Pleistocene crocodylomorphs Pleistocene reptiles of Africa Crocodylidae Holocene extinctions Endemic fauna of Madagascar Crocodylomorphs of Madagascar Prehistoric pseudosuchian genera Fossil taxa described in 2007 Crocodilians of Africa Pleistocene genus first appearances