Crocodylus checchiai

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Crocodylus checchiai
Temporal range: Late Miocene - early Pliocene
lateral view of C. checchiai
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauromorpha
Clade: Archosauriformes
Order: Crocodilia
Family: Crocodylidae
Genus: Crocodylus
Species:
C. checchiai
Binomial name
Crocodylus checchiai
Maccagno, 1947[1]

Crocodylus checchiai is an

extinct species of crocodile from the Miocene to Pliocene of Libya and Kenya. C. checchiai was named in 1947 based on a skull from the Sahabi Formation. Remains from the lower Nawata Formation in the Turkana Basin
of Kenya that were first attributed to the Nile crocodile have now been reassigned to C. checchiai, extending its geographic range. The morphology of the species, in particular the pronounced rostral boss, indicates that it may be the connecting link between African and American species of the genus Crocodylus.

History and naming

The remains of C checchiai were originally described by the Italian paleontologist Angiola Maria Maccagno in 1938. The holotype, an adult skull with an associated mandible, was discovered in the Sahabi Formation and later stored in the Istituto di Paleontologia dell’Università di Roma, where it was then thought to be lost. In the years following, four more skulls were excavated in Libya and stored in the

Nile Crocodile.[3] In an attempt to shed light on the position of the species in Crocodylus, which had previously yielded only unclear phylogenetic results, Delfino and colleagues published a detailed redescription of the taxon in 2020. In the process they rediscovering sn813/lj, the skull used by Maccagno to describe Crocodylus checchiai var. depressa.[4]

Description

Skull in dorsal view

Specimen sn813/lj represents a mesorostral skull with a length of 47 cm (19 in) from the tip of the snout to the end of the

American Crocodile, and unheard of in any other African or Indopacific species of the genus.[4]

Phylogeny and evolution

Live reconstruction of Crocodylus checchiai by D. A. Iurino

Historically the phylogenetic placement of Crocodylus checchiai has only been poorly explored. Earliest attempts at placing the species within Crocodylus largely ignored the rostral boss in spite of its characteristic nature for neotropic species, with Maccagno initially believing it to be closely related to C. palaeindicus based on characters that are currently thought to be of little to no value. Later research conducted by Tchernov and Leakey instead found ties to the extant

Morelet's Crocodile. However, a full phylogenetic analysis was not performed until Brochu & Storrs (2009), who found support for the species inclusion in Crocodylus, but failed to recover its relationship in much more detail due to the formation of a large polytomy.[3] The later analysis conducted by Delfino and colleagues differs from that of Brochu and Storrs in several characters due to the use of the Libyan specimen rather than Tanzanian fossils, which resulted in a better resolved tree finding the taxon to sit at the base of the neotropic clade. This suggests that C. checchiai may be the geographic and phylogenetic link between American Crocodylus species and the ancestral African species. This would shift the dispersal of Crocodylus slightly back in time, but is otherwise consistent with the presumed timeline of the genus' arrival in America (first appearing with Crocodylus falconensis in the Pliocene). C. checchiai may also match the arrival of the genus in Europe, but it's likewise possible that the Italian remains might have come from Asian immigrants.[4]

 Crocodylus 

C. palaeindicus

 Indopacific 

C. palustris

C. siamensis

C. mindorensis

C. porosus

C. johnsoni

C. novaeguineae

 Africa‑New World 

C. niloticus

Crocodylus checchiai

C. intermedius

C. falconensis

C. rhombifer

C. acutus

C. moreletii

A 2018

stratigraphic (fossil age),[5] along with genetic information collected from extinct Voay [6]
produced the tree shown below. In it, C. checchiai differs greatly from its previous placement, forming a clade with C. falconensis outside the clade formed by extant Afro-American taxa.

Crocodylus
Asia+Australia

Crocodylus johnstoni

Crocodylus novaeguineae

Crocodylus mindorensis

Crocodylus porosus

Crocodylus siamensis

Crocodylus palustris

Africa+New World

Crocodylus checchiai†

Crocodylus falconensis†

Crocodylus suchus

Crocodylus niloticus

New World

Crocodylus moreletii

Crocodylus rhombifer

Crocodylus intermedius

Crocodylus acutus

References

  1. ^ Maccagno, A.M. (1947). "Descrizione di una nuova specie di "Crocodilus" del Giacimento di Sahabi (Sirtica)". Atti Accad. Naz. Lincei Mem. Classe Sci. Fis. Mat. Nat. Sez. II Fis. Chim. Geol. Paleontol. Mineral. Ser. VIII. 1 (2): 61–96.
  2. ^ Delfino, M.; Boaz, N.T.; El-Arnauti, A.; Pavlakis, P.; Salem, M. (2008). "New remains of Crocodylus checchiai Maccagno 1947 (Crocodylia, Crocodylidae) from the late miocene of as sahabi, Libya". Garyounis Scientific Bulletin. 5: 111–118.
  3. ^
    S2CID 85103427
    .
  4. ^
    PMID 32703957
    .
  5. PMID 30051855
    .
  6. PMID 33907305
    .
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