Gavialoidea

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Gavialoidea
Temporal range: MaastrichtianPresent
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Possible Cenomanian origin, if "thoracosaurs" are included [1]
Gavialis gangeticus, ZOO Praha 045.jpg
Indian gharial, Gavialis gangeticus
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauromorpha
Clade: Archosauriformes
Order: Crocodilia
Clade: Longirostres
Superfamily: Gavialoidea
Hay, 1930
Subgroups

Gavialoidea is one of three superfamilies of crocodylians, the other two being Alligatoroidea and Crocodyloidea. Although many extinct species are known, only the gharial Gavialis gangeticus and the false gharial Tomistoma schlegelii are alive today, with Hanyusuchus having become extinct in the last few centuries.

Extinct South American gavialoids likely dispersed in the mid Tertiary from Africa and Asia. [4] Fossil remains of the Puerto Rican gavialoid Aktiogavialis puertorisensis were discovered in a cave located in San Sebastián, Puerto Rico and dated to the Oligocene. This individual is thought to have crossed the Atlantic coming from Africa, indicating that this species was able to withstand saltwater. [5]

Classification

Gavialoidea is cladistically defined as Gavialis gangeticus (the gharial) and all crocodylians closer to it than to Alligator mississippiensis (the American alligator) or Crocodylus niloticus (the Nile crocodile). [4] [5] This is a stem-based definition for gavialoids, and is more inclusive than the crown group Gavialidae. [6] As a crown group, Gavialidae only includes the last common ancestor of all extant (living) gavialids and their descendants (living or extinct), whereas Gavialoidea, as a total group, also includes more basal extinct gavialid ancestors that are more closely related to living gavialids than to crocodiles or alligators. When considering only living taxa (neontology), this makes Gavialoidea and Gavialidae synonymous, and only Gavialidae is used. Thus, Gavialoidea is only used in the context of paleontology.

Traditionally, crocodiles and alligators were considered more closely related and grouped together in the taxon Brevirostres, to the exclusion of the gharials. This classification was based on morphological studies primarily focused on analyzing skeletal traits of living and extinct fossil species. [7] However, recent molecular studies using DNA sequencing have rejected Brevirostres upon finding the crocodiles and gavialids to be more closely related than the alligators. [8] [9] [10] [6] [11] The new clade Longirostres was named by Harshman et al. in 2003. [8]

In addition, these recent molecular DNA studies consistently indicate that the false gharial (Tomistoma) (and by inference other related extinct forms) traditionally viewed as belonging to the crocodylian subfamily Tomistominae actually belong to Gavialoidea (and Gavialidae). [8] [12] [13] [9] [10] [6] [11] As its name suggests, the false gharial was once thought to be only distantly related to the gharial despite its similar appearance. The false gharial and other tomistomines were traditionally classified within the superfamily Crocodyloidea as close relatives of crocodiles, based solely on morphological evidence. [12]

The phylogenetic position group of Late Cretaceous-Cenozoic longirostrine eusuchians dubbed the "thoracosaurs" is controversial. Traditionally they are considered to be members of Gavialoidea, but some studies have recovered them as non crocodilian eusuchians. [6]

A 2018 tip dating study by Lee & Yates simultaneously using morphological, molecular (DNA sequencing), and stratigraphic (fossil age) data interpreted inter-relationships within Crocodilia, [6] which was expanded upon in 2021 by Hekkala et al. using paleogenomics by extracting DNA from the extinct Voay . [11] The tip dating analysis resolved the extinct Thoracosaurus and similar extinct close relatives as outside of Gavialoidea.

The below cladogram shows the results of the latest study, and Gavialoidea's relationships within Crocodylia:

Crocodylia
(crown group)

However, other analyses by different authors have continued to resolve thoracosaurs as members of Gavialoidea. [1]

Related Research Articles

<span class="mw-page-title-main">Gavialinae</span> Subfamily of gharial crocodylians

Gavialinae is a subfamily of large semiaquatic crocodilian reptiles, resembling crocodiles, but with much thinner snouts. Gavialinae is one of the two major subfamilies within the family Gavialidae - the other being the subfamily Tomistominae, which contains the false gharial and extinct relatives.

<span class="mw-page-title-main">Gavialidae</span> Family of gharial crocodylians

Gavialidae is a family of large semiaquatic crocodilians with elongated, narrow snouts. Gavialidae consists of two living species, the gharial and the false gharial, both occurring in Asia. Many extinct members are known from a broader range, including the recently extinct Hanyusuchus. Gavialids are generally regarded as lacking the jaw strength to capture the large mammalian prey favoured by crocodiles and alligators of similar size so their thin snout is best used to catch fish, however the false gharial has been found to have a generalist diet with mature adults preying upon larger vertebrates, such as ungulates.

<i>Tomistoma</i> Genus of crocodilians

Tomistoma is a genus of gavialid crocodilians. They are noted for their long narrow snouts used to catch fish, similar to the gharial. Tomistoma contains one extant (living) member, the false gharial, as well as potentially several extinct species: T. cairense, T. lusitanicumT. coppensi, and T. dowsoni. However, these species may need to be reclassified to different genera as studies have shown them to be paraphyletic, for example: previously assigned species T. taiwanicus from Taiwan, is reclassified to the genus Toyotamaphimeia, and T. dowsoni should be excluded from Tomistoma based on phylogenetic analysis.

<i>Boverisuchus</i> Extinct genus of reptiles

Boverisuchus is an extinct genus of planocraniid crocodyliforms known from the middle Eocene of Germany and western North America. It was a relatively small crocodyliform with an estimated total length of approximately 2.2–3.6 metres (7.2–11.8 ft).

<i>Toyotamaphimeia</i> Extinct genus of reptiles

Toyotamaphimeia is a genus of extinct gavialid crocodylian which lived in Japan and Taiwan during the Middle Pleistocene. A specimen recovered in 1964 at Osaka University during the construction of a new science building has been dated to around 430–380 thousand years old based on the stratum in which it was found. Toyotamaphimeia was a fairly large crocodylian measuring approximately 6.3–7.3 metres (21–24 ft) long. Two species are named, T. machikanensis from Japan and T. taiwanicus from Taiwan, both originally described as members of the genus Tomistoma.

<i>Gavialosuchus</i> Extinct genus of reptiles

Gavialosuchus is an extinct genus of gavialoid crocodylian from the early Miocene of Europe. Currently only one species is recognized, as a few other species of Gavialosuchus have since been reclassified to other genera.

<span class="mw-page-title-main">Alligatoroidea</span> Superfamily of reptiles

Alligatoroidea is one of three superfamilies of crocodylians, the other two being Crocodyloidea and Gavialoidea. Alligatoroidea evolved in the Late Cretaceous period, and consists of the alligators and caimans, as well as extinct members more closely related to the alligators than the two other groups.

Dollosuchoides, colloquially known as the Crocodile of Maransart, is an extinct monospecific genus of gavialoid crocodilian, traditionally regarded as a member of the subfamily Tomistominae. Fossils have been found in the Brussel Formation of Maransart, Belgium and date back to the middle Eocene.

<i>Kentisuchus</i> Extinct genus of reptiles

Kentisuchus is an extinct genus of gavialoid crocodylian, traditionally regarded as a member of the subfamily Tomistominae. Fossils have been found from England and France that date back to the early Eocene. The genus has also been recorded from Ukraine, but it unclear whether specimens from Ukraine are referable to Kentisuchus.

Maroccosuchus zennaroi is an extinct gavialoid crocodylian from the Early Eocene of Morocco, traditionally regarded as a member of the subfamily Tomistominae.

Paratomistoma is an extinct monospecific genus of gavialoid crocodylian. It is based on the holotype specimen CGM 42188, a partial posterior skull and lower jaw discovered at Wadi Hitan, Egypt, in Middle Eocene-age rocks of the Gehannam Formation. The skull is unfused but considered morphologically mature. Paratomistoma was named in 2000 by Christopher Brochu and Philip Gingerich; the type species is P. courti in honor of Nicholas Court, who found CGM 42188. They performed a phylogenetic analysis and found Paratomistoma to be a derived member of Tomistominae, related to the false gharial. It may have been a marine or coastal crocodilian.

<i>Planocrania</i> Extinct genus of reptiles

Planocrania is an extinct genus of eusuchian crocodyliforms from what is now China. Two species are currently known to belong to the genus.

<i>Penghusuchus</i> Extinct genus of reptiles

Penghusuchus is an extinct genus of gavialid crocodylian. It is known from a skeleton found in Middle to Upper Miocene rocks of Penghu Island, off Taiwan. The taxon was described in 2009 by Shan and colleagues; the type species is P. pani. It may be related to two other fossil Asian gavialids: Toyotamaphimeia machikanensis of Japan and Hanyusuchus sinensis of South China. It was a medium-sized gavialid with an estimated total length of 4.5 metres (15 ft).

<span class="mw-page-title-main">Crocodyloidea</span> Superfamily of crocodiles

Crocodyloidea is one of three superfamilies of crocodilians, the other two being Alligatoroidea and Gavialoidea, and it includes the crocodiles. Crocodyloidea may also include the extinct Mekosuchinae, native to Australasia from the Eocene to the Holocene, although this is disputed.

Gryposuchinae is an extinct subfamily of gavialid crocodylians. Gryposuchines lived mainly in the Miocene of South America. However, "Ikanogavialis" papuensis may have survived more recently, into the Late Pleistocene/Holocene. Most were long-snouted coastal forms. The group was named in 2007 and includes genera such as Gryposuchus and Aktiogavialis, although a 2018 study indicates that the group might be paraphyletic and rather an evolutionary grade towards the gharial.

<span class="mw-page-title-main">Tomistominae</span> Subfamily of reptiles

Tomistominae is a subfamily of crocodylians that includes one living species, the false gharial. Many more extinct species are known, extending the range of the subfamily back to the Eocene epoch. In contrast to the false gharial, which is a freshwater species that lives only in southeast Asia, extinct tomistomines had a global distribution and lived in estuaries and along coastlines.

<span class="mw-page-title-main">Brevirostres</span> Taxon of reptiles

Brevirostres is a paraphyletic group of crocodilians that included alligatoroids and crocodyloids. Brevirostres are crocodilians with small snouts, and are distinguished from the long-snouted gharials. It is defined phylogenetically as the last common ancestor of Alligator mississippiensis and Crocodylus niloticus and all of its descendants. This classification was based on morphological studies primarily focused on analyzing skeletal traits of living and extinct fossil species, and placed the gharials outside the group due to their unique skull structure, and can be shown in the simplified cladogram below:

Tomistoma cairense is an extinct species of gavialoid crocodilian from the Lutetian stage of the Eocene era. It lived in North East Africa, especially Egypt. Remains of T. cairense have been found in the Mokattam Formation, in Mokattam, Egypt. Tomistoma cairense did not have a Maxilla process within their lacrimal gland, whereas all extant (living) crocodilians do.

Portugalosuchus is an extinct genus of eusuchian crocodyliform that was possibly a basal crocodylian – if so then it would be the oldest known crocodylian to date. The type species is P. azenhae, described in 2018, and it is known from the Late Cretaceous (Cenomanian)-aged Tentugal Formation in Portugal. A 2021 morphological study recovered Portugalosuchus within Crocodylia as a member of Gavialidae closely related to similar "thoracosaurs", while also noting that it might also possibly be outside of Crocodylia completely. A 2022 tip dating analysis incorporating both morphological and DNA data placed Portugalosuchus outside of Crocodylia, as the sister taxon of the family Allodaposuchidae. A cladogram simplified after that analysis is shown below:

<span class="mw-page-title-main">Longirostres</span> Clade of crocodilians

Longirostres is a clade of crocodilians that includes the crocodiles and the gavialids, to the exclusion of the alligatoroids. Defined in 2003 by Harshman et al., Longirostres is a crown group defined phylogenetically as including the last common ancestor of Crocodylus niloticus and Gavialis gangeticus and all of its descendants.

References

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  2. Jouve, S.; de Muizon, C.; Cespedes-Paz, R.; Sossa-Soruco, V.; Knoll, S. (2020). "The longirostrine crocodyliforms from Bolivia and their evolution through the Cretaceous–Palaeogene boundary". Zoological Journal of the Linnean Society. 192 (2): 475–509. doi:10.1093/zoolinnean/zlaa081.
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