Osteolaeminae

Osteolaeminae Temporal range: Eocene–Holocene, 38–0 Ma PreꞒ Ꞓ O S D C P T J K Pg N
West African dwarf crocodile (Osteolaemus tetraspis)
Central African slender-snouted crocodile (Mecistops leptorhynchus)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Archosauromorpha
Clade:	Archosauriformes
Order:	Crocodilia
Family:	Crocodylidae
Subfamily:	Osteolaeminae Brochu, 2003
Genera
Osteolaemus Mecistops? †Aldabrachampsus? †Brochuchus †Euthecodon †Kinyang[1] †Rimasuchus

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).^[2][3] 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.^[4]

Phylogeny

The cladogram below is based on two studies that combined morphological, molecular (DNA sequencing), and stratigraphic (fossil age) data.^[5][6]

Crocodylidae

Osteolaeminae Mecistops cataphractus West African slender-snouted crocodile Euthecodon† Brochuchus† Rimasuchus† Osteolaemus osborni Osborn’s dwarf crocodile Osteolaemus tetraspis Dwarf crocodile Crocodylinae Voay† Crocodylus Crocodylus anthropophagus† Crocodylus thorbjarnarsoni† Crocodylus palaeindicus† Crocodylus Tirari Desert† Crocodylus johnstoni Freshwater crocodile Crocodylus novaeguineae New Guinea crocodile Crocodylus mindorensis Philippine crocodile Crocodylus porosus Saltwater crocodile Crocodylus siamensis Siamese crocodile Crocodylus palustris Mugger crocodile Crocodylus checchiai† Crocodylus falconensis† Crocodylus suchus West African crocodile Crocodylus niloticus Nile crocodile Crocodylus moreletii Morelet's crocodile Crocodylus rhombifer Cuban crocodile Crocodylus intermedius Orinoco crocodile Crocodylus acutus American crocodile

(crown group)

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,^[3][7] as shown in the cladogram below.^[7]

Crocodylidae	Osteolaeminae Rimasuchus lloydi† Voay robustus† Osteolaemus osborni Osborn’s dwarf crocodile Osteolaemus tetraspis Dwarf crocodile "Crocodylus" gariepensis† Brochuchus parvidens† Brochuchus pigotti† Euthecodon arambourgi† Euthecodon brumpti† Crocodylinae Mecistops cataphractus West African slender-snouted crocodile Crocodylus thorbjarnarsoni† Crocodylus anthropophagus† Crocodylus niloticus Nile crocodile Crocodylus checchiai† Crocodylus moreletii Morelet's crocodile Crocodylus intermedius Orinoco crocodile Crocodylus acutus American crocodile Crocodylus rhombifer Cuban crocodile Crocodylus palaeindicus† Crocodylus palustris Mugger crocodile Crocodylus ossifragus† Crocodylus siamensis Siamese crocodile Crocodylus mindorensis Philippine crocodile Crocodylus johnstoni Freshwater crocodile Crocodylus porosus Saltwater crocodile Crocodylus raninus Borneo crocodile Crocodylus novaeguineae New Guinea crocodile	Paleoafrican Crocodylus Neotropical Crocodylus Indo-Pacific Crocodylus

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.)^[4]
  • 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)

References

1. Brochu, Christopher A.; de Celis, Ane; Adams, Amanda J.; Drumheller, Stephanie K.; Nestler, Jennifer H.; Benefit, Brenda R.; Grossman, Aryeh; Kirera, Francis; Lehmann, Thomas; Liutkus-Pierce, Cynthia; Manthi, Fredrick K.; McCrossin, Monte L.; McNulty, Kieran P.; Nyaboke Juma, Rose (2022). "Giant dwarf crocodiles from the Miocene of Kenya and crocodylid faunal dynamics in the late Cenozoic of East Africa". The Anatomical Record. 305 (10): 2729–2765. doi:10.1002/ar.25005. ISSN 1932-8486. PMC 9541231. PMID 35674271.
2. Brochu, C. A.; Storrs, G. W. (2012). "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. Bibcode:2012JVPal..32..587B. doi:10.1080/02724634.2012.652324. S2CID 85103427.
3. 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.
4. Eaton, Mitchell J.; Andrew Martin; John Thorbjarnarson; George Amato (March 2009). "Species-level diversification of African dwarf crocodiles (Genus Osteolaemus): A geographic and phylogenetic perspective". Molecular Phylogenetics and Evolution. 50 (3): 496–506. doi:10.1016/j.ympev.2008.11.009. PMID 19056500.
5. 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.
6. 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. 4 (1): 505. doi:10.1038/s42003-021-02017-0. ISSN 2399-3642. PMC 8079395. PMID 33907305.
7. 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. doi:10.13130/2039-4942/15771.