Crocodylus megarhinus
Encyclopedia
"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.
"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."
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.
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:
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of crocodile
Crocodile
A crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all extant members of the order Crocodilia: i.e...
from the Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
of Egypt
Egypt
Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
. A partial skull was found by British paleontologist Charles William Andrews
Charles William Andrews
Charles William Andrews F.R.S., was a British palaeontologist whose career as a vertebrate paleontologist, both as a curator and in the field, was spent in the services of the British Museum, Department of Geology.-Biography:...
in the Fayum Depression. Andrews named Crocodylus megarhinus in 1905 on the basis of the holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
skull. A complete skull was also uncovered from Egypt in 1907 but was not recognized as "C." megarhinus until 1927.
"C." megarhinus shares many features with living crocodiles like the Nile crocodile
Nile crocodile
The Nile crocodile or Common crocodile is an African crocodile which is common in Somalia, Ethiopia, Uganda, Kenya, Egypt, Tanzania, Zambia, Zimbabwe, Gabon, South Africa, Malawi, Sudan, Botswana, and Cameroon...
(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."
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
Slender-snouted Crocodile
The African Slender-snouted Crocodile is a species of crocodile. Recent studies in DNA and morphology suggest that it may belong in its own genus, Mecistops, but at present most continue to use Crocodylus for this species.African Slender-snouted Crocodile are native to freshwater habitats in...
than the Nile crocodile. "C." articeps has recently been synonymized with "C." megarhinus, and may represent a less mature form in the species' population.
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
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
crocodyline outside the genus but still more closely related to it than the false gharial
False gharial
The false gharial , also known as the Malayan gharial, false gavial, or Tomistoma is a freshwater crocodile of the Crocodylidae family with a very thin and elongated snout...
or mekosuchines
Mekosuchinae
Mekosuchinae was a subfamily of crocodiles from Australia and the South Pacific that have now become extinct. They first appear in the fossil record in the Eocene in Australia, and survived until the Pleistocene in Australia and until the arrival of humans in the Pacific islands of Fiji, New...
. Below is a cladogram
Cladogram
A cladogram is a diagram used in cladistics which shows ancestral relations between organisms, to represent the evolutionary tree of life. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational...
modified from Puértolas et al. (2011) showing its phylogenetic placement among crocodiles: