"Crocodylus" megarhinus is an extinct species of crocodile from the Eocene of Egypt. A partial skull was found by British paleontologist Charles William Andrews in the Fayum Depression. Andrews named Crocodylus megarhinus in 1905 on the basis of the holotype skull. A complete skull was also uncovered from Egypt in 1907 but was not recognized as "C." megarhinus until 1927.^[1]

"C." megarhinus shares many features with living crocodiles like the Nile crocodile (C. niloticus), including a robust triangular skull that is shorter than most other crocodiles. Similarities are also seen in the teeth of the two species. Like living crocodiles, "C." megarhinus has several constricted areas along the upper jaw that provide spaces for the teeth of the lower jaw when the mouth is closed. The proportions of "C." megarhinus and C. niloticus are so similar that American paleontologist Charles C. Mook considered it "very probable that C. megarhinus is a direct ancestor of C. niloticus."^[1]

A second Fayum crocodilian, "Crocodylus" articeps, was named alongside "C." megarhinus. Andrews distinguished "C." articeps from "C." megarhinus on the basis of its narrower snout, which is more similar to the Slender-snouted crocodile than the Nile crocodile. "C." articeps has recently been synonymized with "C." megarhinus, and may represent a less mature form in the species' population.^[2]

Although it has traditionally been described as a species of Crocodylus, "C." megarhinus has been placed outside the genus in many recent phylogenetic analyses. A new genus has not yet been erected for the species. "C." megarhinus is usually found to be a basal crocodyline outside the genus but still more closely related to it than the false gharial or mekosuchines. Below is a cladogram modified from Puértolas et al. (2011) showing its phylogenetic placement among crocodiles:^[3]

References

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Deuterostomia

Crocodylus is one of three genera from the Crocodylinae subfamily extending from the Crocodylidae family.

Established species include four extinct species:^[1]

• † Crocodylus anthropophagus is an extinct crocodile from Plio-Pleistocene of Tanzania.
• † Crocodylus checchiai is an extinct crocodile from Late Miocene of Kenya.
• † Crocodylus palaeindicus is an extinct crocodile the Miocene to the Pleistocene of southern Asia.
• † Crocodylus thorbjarnarsoni is an extinct crocodile from Plio-Pleistocene of Kenya.

The 13 living species are:

• American crocodile, Crocodylus acutus
• Slender-snouted crocodile, Crocodylus cataphractus - studies in DNA and morphology suggest this species may be more basal than Crocodylus and therefore belongs in its own genus, Mecistops.^[2][3][4][1]
• Orinoco crocodile, Crocodylus intermedius
• Freshwater crocodile, Crocodylus johnsoni
• Philippine crocodile, Crocodylus mindorensis
• Morelet's crocodile or Mexican crocodile, Crocodylus moreletii
• Nile crocodile or African crocodile, Crocodylus niloticus (the subspecies found in Madagascar is sometimes called the black crocodile)
• New Guinea crocodile, Crocodylus novaeguineae
• Mugger crocodile, marsh crocodile, or Indian crocodile, Crocodylus palustris
• Saltwater crocodile or estuarine crocodile, Crocodylus porosus
• Cuban crocodile, Crocodylus rhombifer
• Siamese crocodile, Crocodylus siamensis
• Desert crocodile, Crocodylus suchus

• Crocodylus raninus (Considered as a synonym of Crocodylus porosus, its status remains unclear.^[5])

Phylogeny

The cladogram below follows the topology from a 2011 analysis of mitochondrial DNA sequences by Robert W. Meredith, Evon R. Hekkala, George Amato and John Gatesy.^[4]

The cladogram below follows the topology from a 2012 analysis of morphological traits by Christopher A. Brochu and Glenn W. Storrs. Many extinct species of Crocodylus might represent different genera. C. suchus was not included, because its morphological codings were identical to these of C. niloticus. However, the authors suggested that it could be explained by their specimen sampling, and considered the two species to be distinct.^[1]

References

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