''Euthecodon'' is an
extinct
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of long-snouted
crocodile
Crocodiles (family (biology), family Crocodylidae) or true crocodiles are large semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term crocodile is sometimes used even more loosely to inclu ...
. It was common throughout much of
Africa
Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...
during the
Neogene
The Neogene ( ), informally Upper Tertiary or Late Tertiary, is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago ( Mya) to the beginning of the present Quaternary Period Mya. ...
, with
fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
s being especially common in
Kenya
)
, national_anthem = "Ee Mungu Nguvu Yetu"()
, image_map =
, map_caption =
, image_map2 =
, capital = Nairobi
, coordinates =
, largest_city = Nairobi
, ...
,
Ethiopia
Ethiopia, , om, Itiyoophiyaa, so, Itoobiya, ti, ኢትዮጵያ, Ítiyop'iya, aa, Itiyoppiya officially the Federal Democratic Republic of Ethiopia, is a landlocked country in the Horn of Africa. It shares borders with Eritrea to the ...
, and
Libya
Libya (; ar, ليبيا, Lībiyā), officially the State of Libya ( ar, دولة ليبيا, Dawlat Lībiyā), is a country in the Maghreb region in North Africa. It is bordered by the Mediterranean Sea to the north, Egypt to Egypt–Libya bo ...
. Although superficially resembling that of gharials, the long snout was a trait developed independently from that of other crocodilians and suggests a diet of primarily fish. ''Euthecodon'' coexisted with a wide range of other crocodiles in the areas it inhabited before eventually going extinct during the
Pleistocene
The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...
.
Discovery and naming
The first remains of ''Euthecodon'' were described by French paleontologist
Léonce Joleaud based on material collected by the Bourg de Bozas expedition between 1900 and 1903 in
Ethiopia
Ethiopia, , om, Itiyoophiyaa, so, Itoobiya, ti, ኢትዮጵያ, Ítiyop'iya, aa, Itiyoppiya officially the Federal Democratic Republic of Ethiopia, is a landlocked country in the Horn of Africa. It shares borders with Eritrea to the ...
.
[Joleaud, L. (1920). Sur la présence d'un Gavialide du genre ''Tomistoma'' dans le Pliocène d'eau douce de l'Ethiopie. ''Comptes Rendus de l'Académie des Sciences'' 70:816-818.] These remains, thought to belong to a species of
false gharial, were first described in 1920 under the name ''Tomistoma brumpti''. Later that year René Fourtau described fossils from
Wadi Natrun
Wadi El Natrun (Arabic: "Valley of Natron"; Coptic: , "measure of the hearts") is a depression in northern Egypt that is located below sea level and below the Nile River level. The valley contains several alkaline lakes, natron-rich salt de ...
,
Egypt
Egypt ( ar, مصر , ), officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia via a land bridge formed by the Sinai Peninsula. It is bordered by the Mediter ...
as a new species and genus, ''Euthecodon nitriae''.
[Forteau, R., ed. (1920). ''Contribution à l'étude de vertébrés Miocènes de l'Egypt''. Cairo. Government Press.] Subsequent researchers debated whether the two species were distinct enough to form separate species. Joleaud argued that the rostral proportions were too malleable to separate the two, later going as far as to propose that both specimens should still fall under the genus ''Tomistoma''. Both
Camille Arambourg and
Josef A. Kälin recognized ''Euthecodon'' as a valid species but hesitated to split them into two forms, with Kälin recognizing only ''E. brumpti''.
[Kälin, J. (1955). Crocodilia. ''In:'' J. Piveteau, ed., ''Traité de paléontologie'' 5:695-784. Paris: Masson.] Later both Antunes (1961) and Arambourg and Magnier (1961) came to support both species.
[Arambourg, C. and Magnier, P. (1961). Gisement de vértébres dans le bassin tertiare de Syrte (Lybie). ''Comptes Rendus de l'Académie des Sciences'' 252:1181-1183.] The views of
Oskar Kuhn
Oskar Kuhn (7 March 1908, Munich – 1990) was a German palaeontologist.
Life and career
Kuhn was educated in Dinkelsbühl and Bamberg and then studied natural science, specialising in geology and paleontology, at the University of Munich, fr ...
and
Rodney Steel are less clear, as their publications contain contradictions and taxonomic errors.
[Steel, R. (1973). Crocodylia. ''In:'' O. Kuhn, ed., ''Handbuch der Paläoherpetologie'' 16:1-116. Stuttgart. Fischer.][ A third species was described by Ginsburg and Buffetaut in 1978 based on a skull from Gebel Zelten, Libya, which was shorter proportioned than either of the two previously recognized forms. This species was named ''Euthecodon arambourgi'' after Camille Arambourg.][Ginsburg, L. E. and Buffetaut, E. (1978). ''Euthecodon arambourgi'' n. sp. et l'évolution du genera ''Euthecodon'', crocodilien du Néogène d'Afrique. ''Géologie Méditerranéenne'' 5:291-302.]
Description
''Euthecodon'' was a large-bodied crocodilian with an elongated snout similar to that of extant gavialoids. ''Euthecodon'' differs from any other known longirostrine crocodilian in its deeply scalloped rostral margins, each tooth sitting in its own bony sheath, separated from the next by a notable constriction of the rostrum, given the skull a saw-like appearance when viewed from above. The first mandibular teeth occlude outside of the premaxilla and never pierce it as seen in some other crocodilians. The individual teeth are slender, isodont and pointed with two keels (bicarinate), clearly suited for a piscivorous diet. Tooth count varies greatly between species. ''E. arambourgi'', the species with the shortest snout, possesses 19 tooth sockets housing 20 teeth in the upper jaw. Ginsburg and Buffetaut assign 24 upper jaw teeth to ''E. nitriae'' and up to 27 for ''E. brumpti''. The largest specimen from Lothagam possesses 21 teeth in the upper jaw and 20 in the lower, while some specimens from the Pliocene to Pleistocene of Kenya (Koobi Fora) preserve 24 to 25 maxillary teeth opposing 21 to 22 dentary teeth. This difference in tooth count has led some researchers to question whether these specimens, typically assigned to ''E. brumpti'', might actually represent their own species. Unlike any other crocodilians, ''Euthecodon'' typically possess only four premaxillary teeth instead of five, with ''Euthecodon arambourgi'' as an exception, seemingly representing a transitional form in the process of losing the tooth. While still possessing five premaxillary teeth, the second is notably smaller than the rest and shares a single sheath with the third premaxillary tooth. The nasal bone bears a prominent ridge leading up to the eyes, giving its forehead a sloping appearance somewhat similar to that of ''Crocodylus checchiai
''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 Bas ...
''. This form is maintained until the contact between maxilla and premaxilla, where the snout slightly slopes upwards and places the nares on a pedestal. Both the forehead boss and raised nares are most prominent in ''E. brumpti'' and far less developed in either ''E. nitriae'' or ''E. arambourgi''. The nasals are always excluded from any contact to the nares by the premaxilla reaching far back in between the maxilla, meeting the nasal bone at the level of the sixth maxillary tooth. The nasal is fused in some specimens, while others retain it as two distinct bones with visible sutures. Both the prefrontal bones
The prefrontal bone is a bone separating the lacrimal and frontal bones in many tetrapod skulls. It first evolved in the sarcopterygian clade Rhipidistia, which includes lungfish and the Tetrapodomorpha. The prefrontal is found in most modern an ...
and lacrimal bones
The lacrimal bone is a small and fragile bone of the facial skeleton; it is roughly the size of the little fingernail. It is situated at the front part of the medial wall of the orbit. It has two surfaces and four borders. Several bony landmarks o ...
are long and splinter-shaped, with the lacrimals contacting the nasal bones towards the middle or anterior end of the "boss" depending on the specimen. Notably, the skull table of ''Euthecodon'' is comparably small and almost square in shape, with oval supratemporal fenestra (not circular as in gavialoids). Older individuals are known to develop noticeable squamosal ridges or "horns".[Storrs, G. W. (2003). Late Miocene-Early Pliocene crocodilian fauna of Lothagam, southwest Turkana Basin, Kenya. In]
''Lothagam: The Dawn of Humanity in Eastern Africa''
pp. 137–159. New York. Columbia University Press. .[
Some estimates suggest ''Euthecodon'' to be among the largest ]Cenozoic
The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configura ...
crocodilians, if not one of the largest Pseudosuchia
Pseudosuchia is one of two major divisions of Archosauria, including living crocodilians and all archosaurs more closely related to crocodilians than to birds. Pseudosuchians are also informally known as "crocodilian-line archosaurs". Prior to ...
ns, with one specimen (LT 26306), found in Lothagam in the Turkana Basin
An '' Acacia'' tree in the Kokiselei river, northern Kenya
The greater Turkana Basin in East Africa (mainly northwestern Kenya and southern Ethiopia, smaller parts of eastern Uganda and southeastern South Sudan) determines a large endorheic ba ...
, being estimated to have reached a total body length of up to . This specimen's skull alone would have measured .[ Other specimens indicate smaller sizes however. In particular specimen KNM-ER 757 from the Koobi Fora Formation, a skull measuring , was calculated to yield a length of , accounting for a change in proportion in large sized crocodiles. Brochu and Storrs however note that this estimate was achieved by using the proportions of ]nile
The Nile, , Bohairic , lg, Kiira , Nobiin language, Nobiin: Áman Dawū is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa and has historically been considered ...
and saltwater crocodile
The saltwater crocodile (''Crocodylus porosus'') is a crocodilian native to saltwater habitats and brackish wetlands from India's east coast across Southeast Asia and the Sundaic region to northern Australia and Micronesia. It has been listed ...
s, which differ significantly in skull to body ration when compared to longirostrine taxa. Subsequently, these estimates may be exagerating the actual size of Euthecodon in the absence of described postcranial remains.
Species
*''Euthecodon arambourgi''
:Described based on remains from the Miocene of Libya (Gebel Zelten) and Egypt ( Moghara), ''E. arambourgi'' is attested by both sets of remains as having lived during the Burdigalian
The Burdigalian is, in the geologic timescale, an age (geology), age or stage (stratigraphy), stage in the early Miocene. It spans the time between 20.43 ± 0.05 annum, Ma and 15.97 ± 0.05 Ma (million years ago). Preceded by the Aquitanian (sta ...
stage of the Miocene
The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...
, making it the earliest recorded species of ''Euthecodon''. ''Euthecodon arambourgi'' is distinguished from the other two species by its shorter and wider skull and the presence of five premaxillary teeth situated in four tooth sleeves.
*''Euthecodon brumpti''
:''Euthecodon brumpti'' was originally described based on fossil material collected in the Omo Basin of Villafranchian
Villafranchian age ( ) is a period of geologic time (3.5–1.0 Ma) spanning the Late Pliocene and Early Pleistocene used more specifically with European Land Mammal Ages. Named by Italian geologist Lorenzo Pareto for a sequence of terrestrial s ...
(Pliocene to Pleistocene), Ethiopia
Ethiopia, , om, Itiyoophiyaa, so, Itoobiya, ti, ኢትዮጵያ, Ítiyop'iya, aa, Itiyoppiya officially the Federal Democratic Republic of Ethiopia, is a landlocked country in the Horn of Africa. It shares borders with Eritrea to the ...
, with much material later found at other localities throughout East Africa
East Africa, Eastern Africa, or East of Africa, is the eastern subregion of the African continent. In the United Nations Statistics Division scheme of geographic regions, 10-11-(16*) territories make up Eastern Africa:
Due to the historical ...
. These localities include Lothagam
Lothagam is a geological formation located in Kenya, near the southwestern shores of Lake Turkana, from Kanapoi. It is located between the Kerio and Lomunyenkuparet Rivers on an uplifted fault block. Lothagam has deposits dating to the Miocene- ...
(specifically the Nawata
Nawata and Gawata were the Kings of Kano from 1134 to 1136. They were the twin sons of Gijimasu and Munsada.
Reign
The twin kings ruled jointly over Kano until one of them (the ''Kano Chronicle'' did not mention which one of the twins) died 7 mon ...
and Nachukui Formation),[ ]Kanapoi
Kanapoi is a paleontological site in the Kenyan Rift Valley, to the southwest of Lake Turkana. Fossils were first found at Kanapoi in the 1960s by a Harvard expedition, and later by expeditions from the National Museums of Kenya.
Fossils at Kanap ...
, Longarakak, Nakoret and Todenyang. However, according to a 2017 publication by Christopher Brochu, much of the Miocene to Pliocene remains found in the Turkana Basin
An '' Acacia'' tree in the Kokiselei river, northern Kenya
The greater Turkana Basin in East Africa (mainly northwestern Kenya and southern Ethiopia, smaller parts of eastern Uganda and southeastern South Sudan) determines a large endorheic ba ...
may instead belong to an as yet unnamed species, although their anatomy roughly resembles that of ''E. brumpti''. He also mentions the possibility that the species is a junior synonym of ''E. nitriae'', an idea that has also been suggested by past researchers.
*''Euthecodon nitriae''
:The type species of ''Euthecodon'', its fossils were originally found at Wadi Natrun in Egypt (Miocene or Pliocene). Fossils tentatively referred to ''E. cf. nitriae'' have been found in the Upper Miocene (Tortonian
The Tortonian is in the geologic time scale an age or stage of the late Miocene that spans the time between 11.608 ± 0.005 Ma and 7.246 ± 0.005 Ma (million years ago). It follows the Serravallian and is followed by the Messinian.
The Torton ...
) sediments of the Tunisia
)
, image_map = Tunisia location (orthographic projection).svg
, map_caption = Location of Tunisia in northern Africa
, image_map2 =
, capital = Tunis
, largest_city = capital
, ...
n Ségui Formation.
Other remains of ''Euthecodon'' are known from the Miocene Beglia Formation (Tunisia), Early Miocene Rusinga Island
Rusinga Island, with an elongated shape approximately 10 miles (16 km) from end to end and 3 miles (5 km) at its widest point, lies in the eastern part of Lake Victoria at the mouth of the Winam Gulf. Part of Kenya, it is linked to Mbita ...
(Lake Victoria
Lake Victoria is one of the African Great Lakes. With a surface area of approximately , Lake Victoria is Africa's largest lake by area, the world's largest tropical lake, and the world's second-largest fresh water lake by surface area after ...
),[ the ]Albertine Rift
The Albertine Rift is the western branch of the East African Rift, covering parts of Uganda, the Democratic Republic of the Congo (DRC), Rwanda, Burundi and Tanzania.
It extends from the northern end of Lake Albert to the southern end of Lake Tan ...
( Congo),[Pickford, M. (1994). Late Cenozoic crocodiles (Reptilia:Crocodylidae) from the Western Rift, Uganda. ''In:'' B. Senut and M. Pickford, eds., ''Geology and Paleobiology of the Albertine Rift Valley, Uganda-Zaire. Paleobiology/Paléobiologie'' 2(29):137-155. Orléans. Centre International pour la Formation et les Echanges Géologiques.][Aoki, R. (1992). Fossil crocodilians from the Late Tertiary strata in the Sinda Basin, eastern Zaire. ''African Study Monographs'', Supplementary issue ''17'':67-85.] Ombo
Ombo is an island in the municipality of Stavanger in Rogaland county, Norway. The island is the largest island in the Ryfylke region and the second largest island in Rogaland county. There are several villages on the island including Jørstad ...
(Kenya) [Buffetaut, E. (1979). Présence du crocodilien ''Euthecodon'' dans le Miocène inférieur d'Ombo (golfe de Kavirondo, Kenya). ''Bulletin de la Société Géologique de France'' 21:321-322][ and the ]Messinian
The Messinian is in the geologic timescale the last age or uppermost stage of the Miocene. It spans the time between 7.246 ± 0.005 Ma and 5.333 ± 0.005 Ma (million years ago). It follows the Tortonian and is followed by the Zanclean, the first ...
to Zanclean
The Zanclean is the lowest stage or earliest age on the geologic time scale of the Pliocene. It spans the time between 5.332 ± 0.005 Ma (million years ago) and 3.6 ± 0.005 Ma. It is preceded by the Messinian Age of the Miocene Epoch, and fol ...
Sahabi Formation
The Companions of the Prophet ( ar, اَلصَّحَابَةُ; ''aṣ-ṣaḥāba'' meaning "the companions", from the verb meaning "accompany", "keep company with", "associate with") were the disciples and followers of Muhammad who saw or m ...
(Libya
Libya (; ar, ليبيا, Lībiyā), officially the State of Libya ( ar, دولة ليبيا, Dawlat Lībiyā), is a country in the Maghreb region in North Africa. It is bordered by the Mediterranean Sea to the north, Egypt to Egypt–Libya bo ...
). Despite this abundance in northern Africa around the Mediterranean
The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the e ...
, no fossils of ''Euthecodon'' have ever been found outside Africa.
Among the three recognized species, Ginsburg and Buffetaut note a clear evolutionary series from the oldest to youngest species. According to their research, ''Euthecodon'' shows a series of adaptations present in ''E. arambourgi'' and progressively exaggerated in ''E. nitriae'', reaching their peak with ''E. brumpti''. These adaptations include the gradual loss of the second premaxillary tooth, development of additional maxillary teeth, continued lengthening and narrowing of the skull, the exaggeration of a pre-orbital boss spanning the nasal, lacrimal, prefrontal and frontal bones, the raising of the external nares and the prominence of the lacrimal crest. The eyes also face more forward in later species than they do in ''E. arambourgi''. The authors do, however, note that certain traits do not conform to such a direct evolutionary series, and instead appear most prominent in the intermediate ''E. nitriae''. One such example is that in ''E. nitriae'' the prefrontals overflow the orbits, giving them a more circular appearance compared to that of ''E. brumpti''. Ginsburg and Buffetaut suggests that this could be evidence for two possible hypothesis. The first holds on to a continuous lineage, suggesting that the continued rise of the nasal to frontal boss caused a complete reshaping of the region around the orbits, effectively undoing adaptations seen in earlier forms. Their second hypothesis proposes that ''Euthecodon'' split into two lineages, both evolving increasingly longirostral forms but doing so in different ways. This latter interpretation is favored by the fact that ''Euthecodon'' was clearly already present in East Africa by the early Miocene, as indicated by the remains from Ombo and Rusinga Island.[
]
Phylogeny
Although the genus was considered to be a tomistomine gavialoid or even a direct descendant of ''Eogavialis''[Tchernov, E. (1976). Crocodylidae from the Pliocene/Pleistocene formations of the Rudolf Basin. ''In:'' Y. Coppens, F. C. Howell, G. L. Isaac and R. E. Leakey, eds., ''Earliest Man and Environments in the Lake Rudolf Basin: Stratigraphy, Paleoecology, and Evolution'', pp. 370-378. Chicago. University of Chicago Press.][Tchernov, E. (1986). ''Evolution of the Crocodiles in East and North Africa.'' Cahiers de Paléontologie. Paris. Centre National pour la Formation et les Echanges Géologiques.] by early research due to its elongated skull, later research has repeatedly shown this to be merely be the result of convergent evolution
Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
, instead placing it much deeper within the Crocodylidae. For instance, ''Euthecodon'' differs from gavialids and most tomistomines in its small supratemporal fossae and the relatively gradual narrowing of the rostrum (something much more abrupt in gharials).[ Most current analyses place it in ]Osteolaeminae
Osteolaeminae is a subfamily of true crocodiles within the family Crocodylidae containing the dwarf crocodiles and slender-snouted crocodiles, and is the sister taxon to Crocodylinae.
Taxonomy
Osteolaeminae was named by Christopher Brochu in ...
, a family consisting of the extant dwarf crocodile and the extinct '' Rimasuchus'', '' Brochuchus'' as well as possible ''Voay
''Voay'' is an extinct genus of crocodile from Madagascar that lived during the Late Pleistocene to Holocene, containing only one species, ''V. robustus''. Numerous subfossils have been found, including complete skulls, noted for their distinctiv ...
'' and the slender-snouted crocodile
''Mecistops'' is a genus of crocodiles, the slender-snouted crocodiles, native to sub-Saharan Africa.
Taxonomy and etymology
Traditionally placed in ''Crocodylus'', recent studies in DNA and morphology have shown that it is in fact basal to '' ...
.[Brochu, C. and Storrs, G. W. (1995). The giant dwarf crocodile: A reappraisal of ''"Crocodylus" robustus'' from the Quaternary of Madagascar. ''In:'' B. D. Patterson, S. M. Goodman, and J. L. Sedlock, eds., ''Environmental Change in Madagascar''. pp. 6. Chicago. Field Museum.][Brochu, C. (1997). Morphology, fossils, divergence timing, and the phylogenetic relationships of ''Gavialis''. ''Systematic Biology'' 46:479-522.] Phylogenetic analysis utilizing molecular
A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioche ...
(DNA sequencing
DNA sequencing is the process of determining the nucleic acid sequence – the order of nucleotides in DNA. It includes any method or technology that is used to determine the order of the four bases: adenine, guanine, cytosine, and thymine. Th ...
), stratigraphic
Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks.
Stratigraphy has three related subfields: lithostra ...
(fossil age) and morphological data recovers Osteolaeminae, as shown below, with ''Mecistops'' as a close relative of ''Euthecodon''. ''Voay'' was recovered as closer to the genus ''Crocodylus''.
Restricting the analysis to morphological data alone removes ''Mecistops'' from Osteolaeminae and brings ''Voay'' into the family. In this tree ''Euthecodon'' clusters with ''Brochuchus''.
Paleoecology
Although ''Euthecodon'' superficially resembles gharials and likely inhabited a similar niche
Niche may refer to:
Science
*Developmental niche, a concept for understanding the cultural context of child development
*Ecological niche, a term describing the relational position of an organism's species
*Niche differentiation, in ecology, the ...
, its the functional morphology shows some clear differences. Throughout their evolutionary history, many Pseudosuchian groups that evolved elongated skulls (Thalattosuchia
Thalattosuchia is a clade of marine crocodylomorphs from the Early Jurassic to the Early Cretaceous that had a cosmopolitan distribution. They are colloquially referred to as marine crocodiles or sea crocodiles, though they are not members of Cro ...
, Tethysuchia and many gavialoids) also show enlarged supratemporal fossae. Contrary to this connection between fossa size and snout length, however, ''Euthecodon'' has notably small supratemporal fossae, creating only a weak insertion point for the jaw musculature (adductor mandibulae externus profundus muscle). The unique alveolar sleeves likely evolved to at least partly compensate for this, allowing the bodies of the teeth to be much narrower than in other longirostrine taxa. Despite this, however, ''Euthecodon'' would have likely still had a relatively weak bite. The eyes also show clear convergence with gavialoids through different means. To elevate their eyes above the rostrum, derived gharials have increased the circumference of the orbits and enlarged orbital rims, while in ''Euthecodon'' similar results are achieved by raising the entire orbital region. The extremely elongated yet fragile rostrum, trap-like interlocking teeth and raised nares and orbits all indicate a piscivorous diet and aquatic lifestyle, perfected by the Pliocene to Pleistocene ''Euthecodon brumpti''.[
]
''Euthecodon'' was just one of several species within the diverse Crocodilian fauna of Miocene to Pliocene Africa, mirroring similar conditions observed elsewhere during the Miocene (South Americas Pebas Megawetlands and Australia's Riversleigh). In Lothagam
Lothagam is a geological formation located in Kenya, near the southwestern shores of Lake Turkana, from Kanapoi. It is located between the Kerio and Lomunyenkuparet Rivers on an uplifted fault block. Lothagam has deposits dating to the Miocene- ...
, in the southwestern part of the Turkana Basin
An '' Acacia'' tree in the Kokiselei river, northern Kenya
The greater Turkana Basin in East Africa (mainly northwestern Kenya and southern Ethiopia, smaller parts of eastern Uganda and southeastern South Sudan) determines a large endorheic ba ...
, ''Euthecodon brumpti'' coexisted with as many as four different species of crocodiles, including the earliest records of ''Mecistops
''Mecistops'' is a genus of crocodiles, the slender-snouted crocodiles, native to sub-Saharan Africa.
Taxonomy and etymology
Traditionally placed in ''Crocodylus'', recent studies in DNA and morphology have shown that it is in fact basal to ' ...
'', the gharial '' Eogavialis'' and two species of ''Crocodylus'': '' C. checchiai'' and '' C. thorbjarnarsoni''. Of these, ''Euthecodon'' and ''Eogavialis'' are heavily specialised for a piscivorous diet, specialising in preying on smaller fish. ''Mecistops cataphractus'', the modern slender-snouted crocodile, also shows a longirostrine snout morphology, but is more generalist, feeding on amphibians, crustaceans and birds in addition to fish. Such a high number of taxa all coexisting indicates a high degree of niche partinioning supported by favorable environmental conditions and a rich selection of prey items. Fish fossils from Lothagam indicate the presence of Nile perch
The Nile perch (''Lates niloticus''), also known as the African snook, Goliath perch, African barramundi , Goliath barramundi, Giant lates or the Victoria perch, is a species of freshwater fish in family Latidae of order Perciformes. It is wid ...
, bichir
Bichirs and the reedfish comprise Polypteridae , a family of archaic ray-finned fishes and the only family in the order Polypteriformes .Helfman GS, Collette BB, Facey DE, Bowen BW. 2009. The Diversity of Fishes. West Sussex, UK: Blackwell Pub ...
, African lungfish
''Protopterus'' is the genus of four species of lungfish found in Africa. ''Protopterus'' was formerly thought to be the sole genus in the family Protopteridae, but more recent studies have classified it with ''Lepidosiren'' in the family Lepid ...
and electric fish
An electric fish is any fish that can generate electric fields. Most electric fish are also electroreceptive, meaning that they can sense electric fields. The only exception is the stargazer family. Electric fish, although a small minority, in ...
.[
In northern Africa conditions appear similar, with ''Euthecodon arambourgi'' appearing alongside a cast of other crocodilians including the brevirostrine '' Rimasuchus'' and '']Crocodylus checchiai
''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 Bas ...
'' and the longirostrine ''Tomistoma lusitanica
''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 (''Tomistoma schlegelii''), as we ...
'' in both Egypt and Libya. Both Moghara and Gebel Zelten preserve fluvio-marine environments yielding fossils of sharks
Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimorp ...
, dolphins
A dolphin is an aquatic mammal within the infraorder Cetacea. Dolphin species belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontoporiidae (t ...
and sawfish
Sawfish, also known as carpenter sharks, are a family of rays characterized by a long, narrow, flattened rostrum, or nose extension, lined with sharp transverse teeth, arranged in a way that resembles a saw. They are among the largest fish wi ...
alongside catfish
Catfish (or catfishes; order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the three largest species alive, ...
, anthracotheres, carnivorans
Carnivora is a monophyletic order of placental mammals consisting of the most recent common ancestor of all cat-like and dog-like animals, and all descendants of that ancestor. Members of this group are formally referred to as carnivorans, ...
, proboscideans
The Proboscidea (; , ) are a taxonomic order of afrotherian mammals containing one living family (Elephantidae) and several extinct families. First described by J. Illiger in 1811, it encompasses the elephants and their close relatives. Fro ...
and primates
Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians (monkeys and apes, the latter including huma ...
. Gebel Zelten is especially well understood, the environment being reconstructed as rivers banked by tropical forests coming from the south and feeding into a large lagoon, while the intermediate areas are covered by savanna. Although some crocodilians of the area (''Crocodylus'', ''Tomistoma'' and possibly ''Gavialosuchus
''Gavialosuchus'' is an extinct genus of gavialid 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.
Taxonomy
The typ ...
'') have been found on both sides of the Mediterranean, ''Euthecodon'' seemingly never ventured outside of Africa. This may be connected to its specialised lifestyle, preventing it from venturing too far out into saltwater and restricting it to the riverbanks further up river.[ By the time of ''Euthecodon brumpti'', crocodilian diversity had diminished in East Africa compared to that in the older Pliocene records. In Ethiopia ''Euthecodon'' appeared alongside only two other crocodiles, the modern ]Nile crocodile
The Nile crocodile (''Crocodylus niloticus'') is a large crocodilian native to freshwater habitats in Africa, where it is present in 26 countries. It is widely distributed throughout sub-Saharan Africa, occurring mostly in the central, eastern ...
and the slender-snouted crocodile
''Mecistops'' is a genus of crocodiles, the slender-snouted crocodiles, native to sub-Saharan Africa.
Taxonomy and etymology
Traditionally placed in ''Crocodylus'', recent studies in DNA and morphology have shown that it is in fact basal to '' ...
.[ Eventually, increased aridification, increased salinity and conditions favoring more temporary bodies of water may have all contributed to the disappearance of the highly specialised ''Euthecodon'', incapable of sustaining itself or traveling over great enough distances to other bodies of water like the generalist Nile crocodile.][
]
References
External links
''Euthecodon''
in the Paleobiology Database
The Paleobiology Database is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms.
History
The Paleobiology Database (PBDB) originated in the NCEAS-funded Phanerozoic Marine Pale ...
{{Taxonbar, from=Q5414460, from2=Q112779353, from3=Q112779583, from4=Q112779461
Crocodylidae
Miocene reptiles of Africa
Pliocene reptiles of Africa
Pleistocene reptiles of Africa
Miocene crocodylomorphs
Pliocene crocodylomorphs
Pleistocene crocodylomorphs
Prehistoric pseudosuchian genera
Fossil taxa described in 1920