Osteolaeminae Explained

Osteolaeminae is a subfamily of true crocodiles within the family Crocodylidae containing the dwarf crocodiles and slender-snouted crocodiles, and is the sister taxon to Crocodylinae.

Taxonomy

Osteolaeminae was named by Christopher Brochu in 2003 as a subfamily of Crocodylidae separate from Crocodylinae, and is cladistically defined as Osteolaemus tetraspis (the Dwarf crocodile) and all crocodylians more closely related to it than to Crocodylus niloticus (the Nile crocodile).^[1] This is a stem-based definition, and is the sister taxon to Crocodylinae. Osteolaeminae contains the two extant genera Osteolaemus and Mecistops, along with several extinct genera, although the number of extant species within Osteolaeminae is currently in question.^[2]

Phylogeny

The cladogram below is based on two studies that combined morphological, molecular (DNA sequencing), and stratigraphic (fossil age) data.^{[3] [4]}

Alternatively, other morphological studies have recovered Mecistops as a basal member of Crocodylinae, more closely related to Crocodylus than to Osteolaemus and the other members of Osteolaeminae,^{[5] [6]} as shown in the cladogram below.^[6]

Species list

• Subfamily Osteolaeminae
  • Genus Osteolaemus
    • Osteolaemus osborni, Osborn’s dwarf crocodile
    • Osteolaemus tetraspis, dwarf crocodile (There has been controversy as to whether or not this is actually two species; recent (2010) DNA analysis indicate three distinct species: O. tetraspis, O. osborni and a third, currently unnamed.)^[2]
  • Genus Mecistops
    • Mecistops cataphractus, West African slender-snouted crocodile
    • Mecistops leptorhynchus, Central African slender-snouted crocodile
  • Genus Brochuchus
    • Brochuchus pigotti (formerly Crocodylus pigotti)
    • Brochuchus parvidens
  • Genus Euthecodon
    • Euthecodon nitriae
    • Euthecodon brumpti
    • Euthecodon arambourgi
  • Genus Rimasuchus
    • Rimasuchus lloydi (formerly Crocodylus lloydi)

Notes and References

1. Brochu . C. A. . Storrs . G. W. . 10.1080/02724634.2012.652324 . A giant crocodile from the Plio-Pleistocene of Kenya, the phylogenetic relationships of Neogene African crocodylines, and the antiquity of Crocodylus in Africa . Journal of Vertebrate Paleontology . 32 . 3 . 587–602 . 2012 . 2012JVPal..32..587B . 85103427 .
2. Eaton. Mitchell J.. Andrew Martin . John Thorbjarnarson . George Amato . Species-level diversification of African dwarf crocodiles (Genus Osteolaemus): A geographic and phylogenetic perspective. Molecular Phylogenetics and Evolution. March 2009. 50. 3. 496–506. 10.1016/j.ympev.2008.11.009 . 19056500.
3. 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 . . 285 . 1881 . 10.1098/rspb.2018.1071 . 30051855 . 6030529 . free.
4. Hekkala . E. . Gatesy . J. . Narechania . A. . Meredith . R. . Russello . M. . Aardema . M. L. . Jensen . E. . Montanari . S. . Brochu . C. . Norell . M. . Amato . G. . 2021-04-27 . Paleogenomics illuminates the evolutionary history of the extinct Holocene "horned" crocodile of Madagascar, Voay robustus . Communications Biology . en . 4 . 1 . 505 . 10.1038/s42003-021-02017-0 . 33907305 . 8079395 . 2399-3642 . free.
5. 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 . . 9 . e12094 . 34567843. 10.7717/peerj.12094 . 8428266 . free.
6. Azarra . Beatrice . Boschian . Giovanni . Brochu . Christopher . Delfino . Massimo . Iurino . Dawid Adam . Kimambo . Jackson Stanley . Manzi . Giorgio . Masao . Fidelis T. . Menconero . Sofia . Njau . Jackson K . Cherin . Marco . 2021 . A new cranium of Crocodylus anthropophagus from Olduvai Gorge, northern Tanzania . Rivista Italiana di Paleontologia e Stratigrafia (Research in Paleontology and Stratigraphy) . 127 . 2 . 275–295 . 10.13130/2039-4942/15771 .