Mekosuchus

Mekosuchus is a genus of extinct Australasian crocodiles within the subfamily Mekosuchinae. They are believed to have been made extinct by the arrival of humans on the South Pacific islands where they lived.[2] The species of this genus were small in size, 2 m in maximum length, and terrestrial, making them the last surviving group of fully terrestrial crocodilians,[3] leaving only semi-terrestrial species such as the Cuban crocodile and the dwarves Osteolaemus and Paleosuchus.[4]

Mekosuchus
Temporal range: Oligocene – Holocene,
Mekosuchus inexpectatus mandible
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Crocodilia
Clade: †Mekosuchinae
Genus: †Mekosuchus
Balouet & Buffetaut, 1987
Type species
†Mekosuchus inexpectatus
Balouet & Buffetaut, 1987
Species
  • †M. inexpectatus Balouet & Buffetaut, 1987 (type)
  • †M. kalpokasi Mead et al., 2002
  • †M. sanderi Willis, 2001
  • †M. whitehunterensis Willis, 1997

Fossils of related mekosuchines, such as Trilophosuchus, have been found from Miocene Australia (the earliest known mekosuchine is the Eocene genus Kambara), while Quinkana survived until the arrival of humans.[5] Mekosuchus survived until the Holocene, and their sub-fossils have been found in New Caledonia and Vanuatu.

Species
Life restoration of M. inexpectatus

There are currently four species of Mekosuchus recognised. The first discovered (and youngest) is the type species M. inexpectatus from the Holocene of New Caledonia which became extinct at some point in the last 4,000 years, most likely with the arrival of humans in the archipelago.[6] Mekosuchus had specialized back teeth for cracking mollusk shells and arthropod carapaces, an adaptation in response to the lack of large ground-dwelling prey in New Caledonia; although it was likely also an opportunistic hunter that went after lizards and various-sized birds when possible.

Another Holocene species is known, M. kalpokasi which lived on the island of Éfaté of Vanuatu approximately 3,000 years ago and likewise disappeared with the arrival of humans.[7]

M. whitehunterensis, the oldest known species, lived during the late Oligocene in Queensland, Australia.[8] M. sanderi also lived in Queensland but later, during the Miocene.[1]

Phylogeny

A 2018 tip dating study by Lee & Yates simultaneously using morphological, molecular (DNA sequencing), and stratigraphic (fossil age) data established the inter-relationships within Crocodylia.[9] The cladogram below shows the placement of Mekosuchus within Mekosuchinae:[9]

Crocodylia

Alligatoroidea

Prodiplocynodon†

Asiatosuchus†

"Crocodylus" affinis†

"Crocodylus" depressifrons†

"Crocodylus" acer†

Brachyuranochampsa†

Mekosuchinae

Australosuchus†

Kambara taraina†

Kambara implexidens†

Kambara murgonensis†

Kalthifrons†

Paludirex†

Baru wickeni†

Baru darrowi†

Baru Alcoota†

Bullock Creek taxon†

Baru huberi†

Volia†

Mekosuchus†

Trilophosuchus†

Quinkana†

Longirostres
Crocodyloidea

"Crocodylus" megarhinus†

Crocodylidae

Gavialoidea

extinct basal Gavialoids†

Gavialidae

Gavialis

Tomistoma

See also

References
  1. Rio, Jonathan P.; Mannion, Philip D. (6 September 2021). "Phylogenetic analysis of a new morphological dataset elucidates the evolutionary history of Crocodylia and resolves the long-standing gharial problem". PeerJ. 9: e12094. doi:10.7717/peerj.12094. PMC 8428266. PMID 34567843.
  2. Cf. The Recently Extinct Plants and Animals Database: Extinct Reptiles: Mekosuchus inexpectatus Archived 4 March 2016 at the Wayback Machine, noting Anderson, Atholl, Sand, Christophe, Petchey, Fiona and Worthy, Trevor H. (2010). "Faunal Extinction and Human Habitation in New Caledonia: Initial Results and Implications of New Research at the Pindai Caves", Journal of Pacific Archaeology 1.1: 89–109; M. kalpokasi, sp. nov.(J.I. Mead, D.W. Steadman, et al., "New extinct Mekosuchine crocodile from Vanuatu, South Pacific", Copeia, 2002.3: "the extinction of M. kalpokasi and other insular mekosuchines may have been anthropogenic"); .
  3. "Croco eusuchia". Paleopedia.free.fr. Archived from the original on 8 February 2012. Retrieved 23 May 2012.
  4. Darren Naish, "Tetrapod Zoology" (Scientific American blog): "Dissecting a crocodile", 2012
  5. Roberts, R.G., Flannery, T.F., Ayliffe, L.K., Yoshida, H., Olley J.M., Prideaux, G.J., Laslett, G.M., Baynes, A., Smith, M.A., Jones, R., Smith, B.L. (2001). New Ages for the Last Australian Megafauna: Continent-Wide Extinction About 46,000 Years Ago. Science 292 (5523): 1888–1892. DOI: 10.1126/science.1060264
  6. Anderson, Atholl; Sand, C; Petchey, F; Worthy, T. H (2010). "Faunal extinction and human habitation in New Caledonia: Initial results and implications of new research at the Pindai Caves". Journal of Pacific Archaeology. 1 (1). Retrieved 23 February 2021.
  7. Spriggs, Matthew; Bedford, Stuart. "The Archaeology of Vanuatu: 3,000 Years of History across Islands of Ash and Coral". Oxford Handbooks Online. Oxford University Press. Retrieved 22 August 2020.
  8. Mead, Jim I; Steadman, David W; Bedford, Stuart H; Bell, Christopher J; Spriggs, Matthew (21 August 2002). "New Extinct Mekosuchine Crocodile from Vanuatu, South Pacific". Copeia. 2 (3): 632. doi:10.1643/0045-8511(2002)002[0632:NEMCFV]2.0.CO;2. Retrieved 23 February 2021.
  9. Michael S. Y. Lee; Adam M. Yates (27 June 2018). "Tip-dating and homoplasy: reconciling the shallow molecular divergences of modern gharials with their long fossil". Proceedings of the Royal Society B. 285 (1881). doi:10.1098/rspb.2018.1071. PMC 6030529. PMID 30051855.
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