The genus Coloborhynchus is a pterodactyloid pterosaur that is a member of the Anhangueridae family, while other research have recovered it as a member of the Ornithocheiridae. Coloborhynchus is known from the Lower Cretaceous of England (Valanginian age, 140–136 million years ago), and it may also be from the Albian and Cenomanian eras (113–93.9 million years ago), depending on which species are included. It was formerly believed that Coloborhynchus was the biggest known toothed pterosaur, but Tropeognathus, a closely related species, is considered to have had a longer wingspan.
History
Similar to several other ornithocheiroid pterosaurs given names in the 1800s, Coloborhynchus's categorization history is incredibly complex. Many species have been classified to it throughout the years, and different researchers have frequently switched species between Coloborhynchus and allied genera. Richard Owen designated a species, Coloborhynchus clavirostris, in 1874, based on holotype BMNH 1822, a partial snout from the Hastings Beds of the Wealden Group of East Sussex, England. Owen rejected the formation by Harry Govier Seeley of the genus Ornithocheirus. In regard to the fossil's eroded and damaged state, the genus name "maimed beak" refers to it; in contrast, the specific name "key snout" refers to its cross-sectional structure. While he did not name any of these three as the type species, Owen also reclassified Ornithocheirus cuvieri and O. sedgwickii as species under the genus Coloborhycnhus. Owen believed that the position of the front tooth pairs high on the side of the upper jaws defined the genus. Reginald Walter Hooley, however, came to the conclusion in 1913 that the genus was identical to Criorhynchus simus, the second genus and species Owen had established in 1874, and that its site was an artifact of erosion. Owen had reassigned the two former Ornithocheirus species, retaining them in that genus, but Hooley had disregarded this. Kuhn concurred with Hooley in 1967 that Criorhynchus simus and Coloborhynchus clavirostris were synonyms. In addition, Kuhn was the first to properly identify one of the Ornithocheirus species as the type species of the genus, instead of C. clavirostris. The majority of subsequent scholars adopted similar viewpoints, considering Coloborhynchus to be inferior to Criorhynchus in validity. This was altered in 1994 when Yuong-Nam Lee gave the name Coloborhynchus wadleighi to a snout discovered in the Paw Paw Formation of Texas during the Albian era in 1992. The genus's resurgence required a reassessment of a number of similar species that had previously been allocated to different genera in order to ascertain whether or not they truly belonged to Coloborhynchus. The essential characteristics of Coloborhynchus were reformulated in 2008 by Taissa Rodrigues and Alexander Kellner, mostly based on the distinct locations of the tooth sockets. Rodrigues and Kellner contended that Lee's C. wadleighi, which was from an older era and differed from C. clavirostris in several aspects of the skull and teeth, should have been in its own genus, which they called Uktenadactylus. In 2001, Fastnacht classified a fragmentary lower jaw from the Romualdo Member of the Santana Formation in Brazil, which was previously known as Tropeognathus robustus, as Coloborhynchus robustus. David Unwin endorsed this view in 2002 and also equated C. robustus with the better popular species Anhanguera piscator. However, Rodrigues and Kellner disagreed with this categorization, pointing out that none of them had the characteristic sideways pointed teeth or straightening crest starting at the tip of the snout found in C. clavirostris. Rather, Anhanguera piscator and Anhanguera robustus were considered legitimate species of Anhanguera by Rodrigues and Kellner. Coloborhynchus spielbergi is the name given by Veldmeijer in 2003 to another species from the Romualdo Member that is found in Brazil. It is similar to C. clavirostris in one or two characteristics (such a flattened top surface of the snout), but Rodrigues and Kellner considered these similarities questionable and pointed out that they are also seen in other genera. In 2006, Kellner reassembled it as Anhanguera spielbergi. Similar to this, Kellner removed C. araripensis, which was formerly included in the genus Santanadactylus, from the group due to the absence of similar diagnostic characteristics. Siroccopteryx moroccensis was placed under Coloborhynchus by Unwin in 2001 due to its resemblance to C. wadleighi, the type species of Uktenadactylus. According to Fastnacht (2001), Siroccopteryx lacks the distinctive features of the tooth row, much like the other species belonging to Coloborhynchus. Kellner, who recognized Uktenadactylus as a new genus in 2008, likewise considered Siroccopteryx to be different. Unwin (2001) also reclassified to Coloborhynchus the two other species found in the Cambridge Greensand: C. capito and C. sedgwickii, the latter of which Richard Owen (1874) claimed to be one of the genus's founding members. According to Kellner, there is disagreement about the exact categorization of C. capito since it is too incomplete to be compared in its entirety to C. clavirostris. He pointed out that C. sedgwicki could be a member of the same genus as "Ornithocheirus" compressirostris (=Lonchodectes), as it lacks the distinctive characteristics of C. clavirostris, including a crest. The majority of the other species in Coloborhynchus were either placed in different genera or designated as nomina dubia by Rodrigues and Kellner (2013), who believed that the genus was monotypic and only included C. clavirostris. In 2018, Jacobs et al. provisionally classified another specimen from the same site to a separate, unidentified species and designated a new species of Coloborhynchus, C. fluviferox, from the Ifezouane Formation of the Kem Kem Group of Morocco based on a partial snout. A 2020 study by Holgado and Pêgas of Coloborhynchinae transferred C. capito and C. fluviferox to a new genus, Nicorhynchus, and assigned the Ifezouane Formation coloborhynchine, which was previously unidentified, to N. fluviferox. Nonetheless, a 2023 analysis of Kem Kem pterosaurs concluded that the characteristics that set Nicorhynchus apart from Coloborhynchus apart were inconspicuous enough to warrant their synonymy, adding that the evidence was sufficiently fragmented and degraded to corroborate this conclusion.
List of Species and Synonyms
Species which have been assigned to Coloborhynchus by various scientists over the years include:
C. clavirostris Owen, 1874, the type species
?C. ligabuei (Dalla Vecchia, 1993) = Cearadactylus ligabuei Dalla Vecchia, 1993 [also classified as Anhanguera ligabuei]
?C. piscator (Kellner & Tomida, 2000) = Anhanguera piscator Kellner & Tomida, 2000 [also classified as Anhanguera or C. robustus]
C. cuvieri (Bowerbank, 1851) = Ornithocheirus cuvieri (Newton, 1888) = Pterodactylus cuvieri Bowerbank, 1851 [now classified as Cimoliopterus]
C. sedgwicki (Owen 1859) = Ornithocheirus sedgwicki (Newton, 1888) = Pterodactylus sedgwickii Owen, 1859 [now classified as Aerodraco]
C. araripensis (Wellnhofer, 1985) = Santanadactylus araripensis Wellnhofer, 1985 now seen as a nomen dubium
?C. robustus (Wellnhofer, 1987) = Tropeognathus robustus Wellnhofer, 1987 [now seen as a nomen dubium]
C. wadleighi Lee, 1994 [also classified as Uktenadactylus]
C. moroccensis (Mader & Kellner, 1999) = Siroccopteryx moroccensis Mader & Kellner 1999
C. piscator (Kellner & Tomida, 2000) = Anhanguera piscator Kellner & Tomida, 2000
C. spielbergi Veldmeijer, 2003 [now classified as Maaradactylus]
C. capito (Seeley, 1870) = Ornithocheirus capito Seeley, 1870 = "Ptenodactylus capito" Seeley, 1869 [now classified as Nicorhynchus]
C. fluviferox Jacobs, Martill, Ibrahim & Longrich, 2018 [now classified as Nicorhynchus]
Description
Coloborhynchus' type specimen is only known from a fragmentary upper jaw. Therefore, Coloborhynchus clavirostris can only be distinguished from its cousins by a unique combination of tooth socket placements, according to Rodrigues and Kellner's 2008 re-evaluation of the species. The following three pairs of teeth in Coloborhynchus pointed to the sides, whereas the two front teeth pointed forward and were positioned higher on the jaw than the other teeth. The last two sets of teeth, which had been preserved, faced downhill. And last, under the initial set of teeth, there was a distinctive oval depression. In contrast to the small posterior jaws, the tip of the nose fanned out into a larger rosette, similar to the related Anhanguera and Uktenadactylus. But the rosettes of Coloborhynchus were robust and box-shaped, whereas those of species usually attributed to Anhanguera were rounded and spoon-shaped. In addition, Coloborhynchus had a keel-shaped crest on the front of its jaws with its near relatives. However, unlike its relatives, Coloborhynchus' crest was broad and thinned from base to top. A possible closest related or member of the same genus, Siroccopteryx moroccensis, also has a thickened crest similar to this one. In contrast to its cousins, it also possessed a straight front border that starts at the tip of the snout rather than further back as in other species. Though it has not yet been published, Darren Naish of Brazil reported to paleontologist Alexander Kellner in 2007 that a second specimen exhibiting all of these same distinctive traits. This specimen most likely represents a second specimen of C. clavirostris. The potential species Coloborhynchus capito is the largest known toothed pterosaur and the second largest known ornithocheirid (after a Tropeognathus specimen). A 2011 description of a referenced specimen from the English Cambridge Greensand states that it has an extremely big upper jaw tip displaying the traits of its teeth that set C. capito apart from other species. With teeth that have a base diameter of up to 1.3 cm, the jaw tip is around 10 cm tall and 5.6 cm broad. In the event that the dimensions of this specimen aligned with those of other recognized Coloborhynchus species, the entire length of the head may have reached 75 cm, resulting in an approximate wingspan of 7 meters (23 feet). That being said, this species could be in a distinct genus. A rostrum fragment from the English Wessex Formation is recognized to be diagnostic for Coloborhynchus sp.
Classification
The species Coloborhynchus clavirostris and C. wadleighi (now commonly accepted as Uktenadactylus) are sister taxa to Ornithocheirus simus in the family Ornithocheiridae, according to a topology developed by Andres and Myers in 2013. The family itself is positioned within the more inclusive clade Ornithocheirae. Subsequently, in 2019, Pentland et al. discovered a finding that was comparable to that of Andres and Myers in 2013, indicating that Coloborhynchus is Ornithocheirus' sibling taxon. The left side of their cladogram is displayed. In contrast to Andres and Myers (2013), who placed Coloborhynchus and Siroccopteryx under the Ornithocheiridae, Jacobs et al. (2018) recovered a cladogram that was similar to that of that study. However, in their analysis, they referred to C. wadleighi as Uktenadactylus wadleighi. In 2019, they released their conclusion. Nonetheless, Coloborhynchus has been found in several subsequently conducted examinations in 2019 and 2020, notably in the subfamily Coloborhynchinae of the Anhangueridae family. A phylogenetic study conducted in 2020 by Borja Holgado and Rodrigo Pêgas is displayed in the cladogram on the left.
Topology 1: Pentland et al. (2019).
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Topology 2: Holgado & Pêgas (2020).
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Paleobiology
Coloborhynchus is typically considered a marine piscivore, like other anhanguerids. It was discovered in a research to be present in the carnivorous pterosaur taxa, as contrast to a number of other species that are piscivore and insectivore.
Coloborhynchus reconstruction.
Jaw holotype of Coloborhynchus.
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