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Nile Crocodiles (Crocodylus niloticus & C. suchus) Fact Sheet: Taxonomy & History

Taxonomic History and Nomenclature

Common names

  • Nile Crocodile
  • African common names (from Harper 2001)
    • Mamba, in Swahli
    • Garwe, in Shona

Scientific name

  • Etymology (from Parker 2009)
    • Genus Crocodylus derived from two Greek word kroko meaning "pebble" and deilos meaning "worm"
      • Referring to the rough texture of the skin
      • Herodotus used "krokodilos" to describe a lizard in the Ionic dialect of Greek
      • Later, Ionians applied this term to creatures in Egypt they thought similar
    • Specific epithet niloticus in reference to the Nile River in Africa
  • Subspecies
    • 7 proposed; none officially recognized (Britton 2009)
      • Geographical races distinguished mainly by features of their scales (from Trutnau & Sommerlad 2006)
        • Variation in numbers, shape, and degree of ossification
      • Newly rediscovered dwarfed crocodiles
        • Inhabit Mauritania
        • Previously considered extirpated
        • Believed to be Nile Crocodiles by some
          • Others consider them distinctive, based on DNA analysis (Schmitz et al. 2003)
            • Assigned the scientific name Crocodylus suchus (Trutnau & Sommerlad 2006)

Evolutionary History

Position within Reptilia

  • Considered diapsids (Benton 1984)
    • Have two skull openings behind the eye socket, each of which is roofed by a bony arch
      • By modern classification systems, birds are also considered diapsids, although their skull have been highly modified
      • Other vertebrates such as mammals are synapsids (one opening) or anapsids such as turtles (no openings)
    • Diapsid subdivisions
      • Archosauria ("ruling replies")
        • Includes modern birds and crocodiles as well as extinct dinosaurs, pterosaurs
      • Lepidosauria
        • Includes lizards and snakes
  • Relationship with birds
    • Birds diverged from crocodile-like animals c. 254 million years ago (Mya) (Janke & Arnason 1997)

Order Crocodylia

  • Ancestors
    • Modern crocodiles descend within the reptiles c. 225 Mya (from Summers 2005; Seymour et al. 2004; Carroll 1988)
      • Forerunners similar to the small, active, and bipedal land-based predator Saltoposuchus
        • Active, warm-blooded, land-living ancestor
          • Later adapted a largely aquatic way of life, leaving terrestrial habitats to the dinosaurs
      • Arose in the Late Triassic
      • Geographic distribution
        • Europe, South America, and South Africa
    • Sarcosuchus, a distant crocodile-relative, lived in Africa c.110 million years ago (Cretaceous) (from Sereno 2001)
      • Animal reached lengths up to twice that of the largest living crocodiles or 12 m (c. 40 ft)
  • Crocodile divergence
    • Crocodiles, alligators, and caimen branched c. 65 Mya, according to fossil and molecular data
      • Closest living relatives
        • Birds more closely related to crocodiles than to the lizards (Janke & Arnason 1997)
          • Molecular data (similar protein coding genes) and other evidence support this relationship (Janke & Arnason 1997)
        • Lepidosaurs (spiny lizards such as Tuatara of New Zealand) and other lizards and snakes are more distantly related to dinosaurs (Benton 1984)
    • Historic distribution
      • Existed on every continent, except Antarctica, by c. 65 Mya

Family Crocodylidae

  • Diversification
    • Crocodiles and alligators diverged c.140 Mya (Jurassic/Cretaceous boundary) (Janke et al 2005)
    • Modern species of crocodiles began to be distinct around 5-7 Mya (Late Miocene) (Brochu 2001)

Genus Crocodylus

  • Origin
    • Fossil remains date to 5-7 Mya, in Africa
  • Fossil record of Nile Crocodile
    • Date to 2.5-3.5 Mya (Late Pliocene), in North and East Africa (Trutnau & Sommerlad 2006)
  • Diversity within C. niloticus
    • Modern populations geographically unique
      • Modern genetic testing supports "distinct evolutionary lineages" within the species (from Hekkala et al 2009)
      • Unlike the traditional view of a single Nile Crocodile species adapted to a wide geographic range

Cultural History

Crocodile mummies

  • Found in Egyptian tombs (from Trutnau & Sommerlad 2006)
    • In 1827 two crocodile mummies were named by French naturalist Geoffroy Saint Hillaire
      • Crocodylus lacunosus and Crocodylus complanatus

Popular cultural references

  • Documentary appearances
    • Deadly Crocodiles of the Nile River – 2014, National Geographic Wild
    • Nile Crocodiles: Diving with a deadly predator – 2013, CBS
      • Anderson Cooper takes an in depth look at the Nile Crocodile in this 13 minute 60 Minutes clip.

Classification

Kingdom: Animalia

Phylum: Chordata

Class: Reptilia

Order: Crocodylia

Family: Crocodylidae

Genus: Crocodylus

Species*: Crocodylus niloticus - Nile Crocodile (eastern Africa, Nile valley, southern Africa)

Species*: Crocodylus suchus - Nile Crocodile (west and central Africa)

*Note that Hekkala et al. (2011) found that although both species have adjacent ranges in Africa, they are not sister species.

Sources: Hekkala et al. (2011); Grigg and Kirshner (2015)

Egyptian God Sobek

Egyptian god Sobek

Image credit: © Rhys Davenport from Flickr. Some rights reserved.

Page Citations

Benton (1985)
Brochu (2001)
Brochu & Densmore (2001)
Carroll (1988)
Harper (2001)
Hekkala et al (2009)
Janke & Arnason (1997)
Janke & Arnason (2005)
King & Burke (1997)
Parker (2009)
Summers (2005)
Sereno (2001)
Seymour et al (2004)
Trutnau & Sommerlad (2006)

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