Mecistops

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Mecistops
Temporal range:
Ma[1]
West African slender-snouted crocodile
Central African slender-snouted crocodile
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauromorpha
Clade: Archosauriformes
Order: Crocodilia
Family: Crocodylidae
Subfamily: Osteolaeminae
Genus: Mecistops
Gray, 1844
Species
  • Mecistops cataphractus
  • Mecistops leptorhynchus
Range map

Mecistops is a genus of crocodiles, the slender-snouted crocodiles, native to sub-Saharan Africa.

Taxonomy and etymology

Traditionally placed in

M. cataphractus, but recent genetic analysis has revealed the existence of two species: the West African slender-snouted crocodile (M. cataphractus) and the Central African slender-snouted crocodile (M. leptorhynchus). Both species diverged during the Miocene (about 6.5–7.5 million years ago) and are separated by the Cameroon Volcanic Line.[6][7]

Phylogeny

The cladogram below is based on two studies that combined morphological and molecular (DNA sequencing) data.[8][9] (Note that most morphological analyses find a closer relationship between Euthecodon and Brochuchus.[10])

Crocodylidae
Osteolaeminae

Brochuchus†

Rimasuchus†

Osteolaemus osborni

Osborn’s dwarf crocodile

Osteolaemus tetraspis Dwarf crocodile

Crocodylinae

Voay†

Crocodylus

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 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

basal member of Crocodylinae, more closely related to Crocodylus than to Osteolaemus and the other members of Osteolaeminae,[1][10] as shown in the cladogram below.[10]

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 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

Extant Species

Image Scientific name Common name Distribution
Mecistops cataphractus
 (Cuvier, 1825)		 West African slender-snouted crocodile Benin, Burkina Faso, southern Senegal, Gambia, Ghana, Guinea, Guinea-Bissau, Ivory Coast, Liberia, southern Mali, Nigeria, Sierra Leone, and Togo
Mecistops leptorhynchus
 (Bennett, 1835)		 Central African slender-snouted crocodile Cameroon, Equatorial Guinea, Gabon, northern Angola, Central African Republic, Republic of the Congo, Democratic Republic of the Congo

Etymology

The

genus name Mecistops is most probably derived from the Ancient Greek words μήκιστ (mēkist) meaning "longest" and ὄψις (ópsis) meaning "aspect" or "appearance" or ὄψ (óps) meaning 'face'.[7]

Description

Slender-snouted crocodiles are native to freshwater habitats in central and western Africa. They prefer highly vegetated bodies of water to hide from prey and potential predators. They are medium-sized crocodiles, typically slightly smaller than the Nile crocodile, but are larger than several other species of crocodilians. Adults are typically about 2.5 m (8.2 ft) long, but have been known to reach 4.2 m (14 ft).[11][12] They weigh between 125 and 325 kg (276 and 717 lb).[13][14] Males are significantly larger than females. They have a slender snout used for catching prey, hence their name. They are incredibly shy and adversely impacted by human disturbance.

Behavior

Slender-snouted crocodiles bear a superficial resemblance to gharials, which also have a very slender snout

The diet of the slender-snouted crocodile consists mainly of

nesting season than that of the sympatric dwarf crocodile
, which may nest further from the riverine habitat frequented by Mecistops. The breeding season begins in January or February and lasts until July.

Slender-snouted crocodiles lay an average of 16 (minimum 13, maximum 27) very large eggs (relative to body size) about a week after completion of the mound nest. The nests are constructed out of decaying vegetation.

soft-shelled turtles), they apparently are minimal, possibly accounting for the small number of relatively large eggs laid, and the long incubation period. The sex of the eggs is determined by temperature. Females are produced between 28 and 31 °C. Males are produced between 31 and 33 °C. The maximum temperature that the eggs are able to withstand is 34 °C and produce females.[16]
Sex is determined between day 14 and 21. The mothers help the offspring hatch if they can not do so themselves. Hatchlings are precocious and mimic a smaller version of the parents. They also have very sharp teeth for protection.

This genus has good hearing, eyesight, and smell. Throughout the body of crocodiles, sensory pits are present, which have nerve terminals inside. The two types of these sensory pits are integumentary sense organs that cover the body and papillae that cover the head, primarily around the snout. When under water, crocodile have a “third eyelid” called a nictitating membrane, which is present in many other reptiles, but is unique in crocodiles because it is semitransparent and acts as goggles to improve eyesight when hunting and prevents eye damage. Crocodiles are able to make certain sounds, especially juveniles. Hatchling crocodiles are able to indicate when they will hatch by making a vocalization that can be heard by the mother. Crocodiles can make coughing, hissing, and bellowing vocalizations usually when feeling threatened.

Conservation

Both species in the genus have been studied very little, in part due to their remote habitat. However, M. cataphractus (when it contained both the West African and Central African populations) has been classified as

critically endangered by the IUCN. Threats include hunting (skin and bushmeat), habitat loss, overfishing (they mainly feed on fish), and general disturbance. Both species have been entirely extirpated from several countries where formerly present, and have declined elsewhere. However, the Central African species retains a relatively robust population, especially in Gabon.[6] There is considerable uncertainty about the size of the wild population, but it is estimated that between 1,000 and 20,000 remain. Slender-snouted crocodiles are kept and bred at a number of zoos in Europe and North America, and the Ivory Coast
has started a captive-breeding program.

References

  1. ^
    PMID 34567843
    .
  2. PMID 16495085
    .
  3. PMID 20195356
    .
  4. PMID 21459152
    .
  5. S2CID 85103427
    .
  6. ^
    PMID 24335982
    .
  7. ^
    PMID 30486023
    .
  8. PMID 30051855
    .
  9. PMID 33907305
    .
  10. ^
    doi:10.13130/2039-4942/15771
    .
  11. ^ WAZA: Crocodylus cataphractus Archived 2016-10-09 at the Wayback Machine. Retrieved 18 January 2016.
  12. ^ Crocodilians, Natural History & Conservation: Crocodylus/Mecistops cataphractus. Retrieved 18 January 2016.
  13. ^ African Slender-Snouted Crocodile | The Maryland Zoo in Baltimore. Marylandzoo.org. Retrieved on 2014-05-07.
  14. ^ Slender-Snouted Crocodile | San Diego Zoo Animals. Sandiegozoo.org. Retrieved on 2014-05-07.
  15. ISBN 9782880326012
    .
  16. S2CID 23596287
    .
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