Baryonychinae
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Baryonychinae is an extinct
clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
or
subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zo ...
of
spinosaurid Spinosauridae (or spinosaurids) is a clade or Family (taxonomy), family of tetanuran theropod dinosaurs comprising ten to seventeen known genera. Spinosaurid fossils have been recovered worldwide, including Africa, Europe, South America, and Asia. ...
s from the
Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...
of Europe and West Africa. The clade was named by Charig & Milner in 1986 and defined by Sereno et al. in 1998 and Holtz et al. in 2004 as all taxa more closely related to '' Baryonyx walkeri'' than to ''
Spinosaurus aegyptiacus ''Spinosaurus'' (; ) is a genus of large spinosaurid theropod dinosaurs that lived in what now is North Africa during the Cenomanian stage of the Late Cretaceous period, about 100 to 94 million years ago. The genus was known first from ...
''. Baryonychines were large, bipedal predators with elongated, crocodile-like skulls and lower jaw tips fanning out into rosettes bearing conical, often unserrated, teeth, and a distinct premaxillary notch. They possessed robust forelimbs supporting three-fingered hands with an enlarged first digit claw, to which the subfamily name indirectly refers. Members of this group, unlike the more derived
Spinosaurinae Spinosauridae (or spinosaurids) is a clade or family of tetanuran theropod dinosaurs comprising ten to seventeen known genera. Spinosaurid fossils have been recovered worldwide, including Africa, Europe, South America, and Asia. Their remains have ...
, sported only low sails or none at all.


History of discovery

In 1820, paleontologist
Gideon Mantell Gideon Algernon Mantell Membership of the Royal College of Surgeons, MRCS Fellow of the Royal Society, FRS (3 February 1790 – 10 November 1852) was an English obstetrician, geologist and paleontology, palaeontologist. His attempts to reconstr ...
discovered numerous fossil teeth from the Wadhurst Clay Formation of Britain. These were in 1841 named '' Suchosaurus cultridens'' by paleontologist
Richard Owen Sir Richard Owen (20 July 1804 – 18 December 1892) was an English biologist, comparative anatomy, comparative anatomist and paleontology, palaeontologist. Owen is generally considered to have been an outstanding naturalist with a remarkabl ...
, and were identified as a
crocodilian Crocodilia () is an Order (biology), order of semiaquatic, predatory reptiles that are known as crocodilians. They first appeared during the Late Cretaceous and are the closest living relatives of birds. Crocodilians are a type of crocodylomorp ...
. A second species, '' Suchosaurus girardi'', was named in 1897 by Henri-Émile Sauvage from the Papo Seco Formation of Portugal. It was not until the description of ''Baryonyx'' in 1986 that these remains were identified as spinosaurid teeth and ''Suchosaurus'' was placed in the
Spinosauridae Spinosauridae (or spinosaurids) is a clade or Family (taxonomy), family of tetanuran theropod dinosaurs comprising ten to seventeen known genera. Spinosaurid fossils have been recovered worldwide, including Africa, Europe, South America, and Asia. ...
. The second described representative of the subfamily was unearthed in 1983 by fossil collector William John Walker, within the Smokejacks Pit, Weald Clay Formation, Surrey, England. This initiated the involvement of the Natural History Museum of London, discovering a 65% complete skeleton: NHMUK VP R9951. In 1986, the specimen was published and described by Alan J. Charig and Angela C. Milner as '' Baryonyx walkeri'', with a more detailed monograph published in 1997. Teeth, hand bones, and vertebrae attributed to the genus were later discovered in 1998 and 2004. The same year, Spinosaurinae and Baryonychinae were cladistically defined by Holtz and colleagues. In 1973, paleontologist Philippe Taquet discovered specimen MNHN GDF 266 consisting of two premaxillae, a partial maxilla, and a dentary, along with several similar remains from Gadoufaoua, Elrhaz Formation, Niger. They were in 1998 described as the holotype and
paratype In zoology and botany, a paratype is a specimen of an organism that helps define what the scientific name of a species and other taxon actually represents, but it is not the holotype (and in botany is also neither an isotype (biology), isotype ...
s of '' Cristatusaurus lapparenti'', although after several inconclusive debates on whether or not the specimen represents the then newly described ''
Baryonyx ''Baryonyx'' () is a genus of theropod dinosaur which lived in the Barremian stage of the Early Cretaceous period, about 130–125 million years ago. The first skeleton was discovered in 1983 in the Smokejack Clay Pit, of Surrey, England, in ...
''. In 1997,
Paul Sereno Paul Callistus Sereno (born October 11, 1957) is a professor of paleontology at the University of Chicago who has discovered several new dinosaur species on several continents, including at sites in Inner Mongolia, Argentina, Morocco and Niger. ...
and colleagues discovered a ~67% complete skeleton, MNN GDF500, in Gadoufaoua. The next year, Sereno et al. described the specimen as the new baryonychine '' Suchomimus tenerensis''. The species was also the subject of synonymy disputes over ''Cristatusaurus'' and ''Baryonyx'' throughout the 1990s and 2000s. From 2013 to 2020, several spinosaurid fragments were discovered from the
Wessex Formation The Wessex Formation is a fossil-rich England, English geological formation that dates from the Berriasian to Barremian Stage (stratigraphy), stages of the Early Cretaceous. It forms part of the Wealden Group and underlies the younger Vectis Form ...
in Britain. In 2021, Barker et al. described these specimens, IWCMS 2014.95.5, IWCMS 2021.30, IWCMS 2014.95.1-3, IWCMS 2014.95.4, IWCMS 2014.95.6, IWCMS 2014.96.1, 2; 2020.448.1, 2, and IWCMS 2014.96.3, as the two new genera '' Ceratosuchops inferodios'' and '' Riparovenator milnerae''. The study defined a new subclade within Baryonychinae: Ceratosuchopsini, defined as all taxa more closely related to ''Ceratosuchops inferodios'' than to ''Baryonyx walkeri''. According to the performed analysis and clade definition, the group contains ''Ceratosuchops'', ''Riparovenator'', and ''Suchomimus''. A 2025 review of Cretaceous theropods of Africa concluded that the hypodigm of '' Eocarcharia''—a contemporary of ''Suchomimus'' traditionally regarded as a basal carcharodontosaurid—was chimaeric, comprising a single carcharodontosaurian element (an isolated ) and several remains of a spinosaurid: the holotype (an isolated ) and referred skull roof material. Several anatomical characteristics supported baryonychine affinities for the non-maxilla ''Eocarcharia'' material, simultaneously excluding allosauroid affinities. A phylogenetic analysis supported the placement of this taxon within the Ceratosuchopsini, as the sister taxon to ''Suchomimus''. Baryonychines may have been particularly diverse in the Iberian Peninsula, as suggested by the description of multiple new taxa in the early 2020s: '' Iberospinus natarioi'' ( Papo Seco Formation) in 2022, '' Protathlitis cinctorrensis'' ( Arcillas de Morella Formation) in 2023, and '' Riojavenatrix lacustris'' ( Enciso Group) in 2024. Numerous undescribed specimens have been found as well, such as XMDFEC V0010, described in 2010 by Hone, Xu and Wang; a theropod tooth from the
Majiacun Formation The Majiacun Formation is a Santonian to Coniacian geologic formation in China.Megalosauroidea as a whole, well into the
Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...
.Majiacun Formation
at
Fossilworks Fossilworks was a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world. History Fossilworks was cr ...
.org
However, this tooth lacked spinosaurid synapomorphies, and it was reclassified as a sister taxon of a separate theropod family
Abelisauridae Abelisauridae (meaning "Abel's lizards") is a family (or clade) of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are fou ...
in 2023. Other undescribed specimens include UT-JAW2 from Libya and various remains from Spain, such as Baryonychinae indet. from Vallipón, Castellote, Spain, LAD0-2 from Spain CMP-2 from Cantera del Mas de la Parreta 1, from Castilla y Leon, from the El Castellar Formation, Tenadas del Jabali, and from Mas de Curolles.


Description

Even though baryonychines were on average smaller than the more advanced spinosaurines, they were still decently large compared to theropods in general. The smallest members, ''
Ceratosuchops ''Ceratosuchops'' (meaning "horned crocodile face") is a genus of spinosaurid from the Early Cretaceous (Barremian) of Britain. Discovery and naming The holotype remains of this taxon consist of IWCMS 2014.95.5 (premaxillary bodies), IWCM ...
'' and ''
Riparovenator ''Riparovenator'' ("riverbank hunter") is a genus of Baryonychinae, baryonychine spinosaurid dinosaur from the Early Cretaceous (Barremian) period of Britain. The genus contains a Monotypic taxon, single species, ''Riparovenator milnerae''. Di ...
'', are estimated at 8–9 m (26–29 ft) and ~1.4-2 tons, while the largest member, ''
Suchomimus ''Suchomimus'', from Ancient Greek ''σούχος'' (''soúkhos''), meaning "crocodile", and Latin ''mimus'', meaning "actor", is a genus of spinosaurid dinosaur that lived between 125 and 112 million years ago in what is now Niger, North A ...
'', is estimated to measure 9.5–11 m (31 –36 ft) in length and 3–4.7 tons in weight.Holtz, Thomas R. Jr. (2012) ''Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages,'
Winter 2011 Appendix.
/ref> Members of this family, like other spinosaurids, sported robust forelimbs with large, three-clawed hands. However, unlike the more derived spinosaurines, these animals possessed small sails, as in ''Suchomimus'', ''Riparovenator'', and ''Ceratosuchops'' (for the latter two, sails were assumed judging by their phylogenetic position); some with only the vertebrae of the sacral region being elongated, or none at all, as in ''Baryonyx''.


Skull

Like most other spinosaurids, baryonychines had a very elongated skull compared to other theropods. Furthermore, even in comparison to the spinosaurines their skulls were long. Perhaps the most proportionally-lengthened skull belongs to ''
Suchomimus ''Suchomimus'', from Ancient Greek ''σούχος'' (''soúkhos''), meaning "crocodile", and Latin ''mimus'', meaning "actor", is a genus of spinosaurid dinosaur that lived between 125 and 112 million years ago in what is now Niger, North A ...
''. In its very crocodilian skull, there is little to no concavity or convexity from the front (premaxillae) to the back (parietals) of the skull, unlike in spinosaurines and most other theropods. Baryonychines possess reduced antorbital fenestrae in comparison to other theropods, with most of the front snout being solid bone formed by the premaxillae and
maxillae In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxillar ...
. The tips of the premaxillae were expanded into a " terminal rosette" holding enlarged, recurved teeth. Behind these expansions, baryonychines featured a subnarial gap complex where dentary teeth fit into, and, further posterior, a dentary gap that the large anteriormost maxillary teeth indented. These animals also bore reduced, narrow premaxillary crests.


Classification

The subfamily Baryonychinae was first implicitly named in 1986 by Alan J. Charig and Angela Milner when they named the family "Baryonychidae" to include ''
Baryonyx ''Baryonyx'' () is a genus of theropod dinosaur which lived in the Barremian stage of the Early Cretaceous period, about 130–125 million years ago. The first skeleton was discovered in 1983 in the Smokejack Clay Pit, of Surrey, England, in ...
''. Those who name families are considered the nominal authors of the subfamilies also. The family Baryonychidae was invalidated when ''Baryonyx'' was found to be a spinosaurid. Milner stated that it was likely that '' Suchosaurus'' belonged to this subfamily as well. In 1998, the newly described ''
Cristatusaurus ''Cristatusaurus'' is a genus of theropod dinosaur that lived during the Early Cretaceous Geological period, Period of what is now Niger, 112 million years ago. It was a baryonychine member of the Spinosauridae, a group of large Bipedalism, bipe ...
'' was agreed to be very closely related to, if not identical to, ''Baryonyx'' by Charig & Milner, 1986 & 1997, Sereno, 1998, and Rauhut, 2003. Later in 1998, Sereno et al. described the genus ''
Suchomimus ''Suchomimus'', from Ancient Greek ''σούχος'' (''soúkhos''), meaning "crocodile", and Latin ''mimus'', meaning "actor", is a genus of spinosaurid dinosaur that lived between 125 and 112 million years ago in what is now Niger, North A ...
'', and placed it in Baryonychinae along with ''Baryonyx''. They defined the clade's distinguishing characteristics as "numerous small-sized, serrated teeth in the dentary behind the terminal rosette and deeply-keeled anterior dorsal vertebrae." By 2002, the conclusion was that the subfamily contained the genera ''Baryonyx'', ''Cristatusaurus'', ''Suchomimus'', and ''Suchosaurus''. The clade was phylogenetically defined by Holtz et al. as all taxa more closely related to '' Baryonyx walkeri'' than to ''
Spinosaurus aegyptiacus ''Spinosaurus'' (; ) is a genus of large spinosaurid theropod dinosaurs that lived in what now is North Africa during the Cenomanian stage of the Late Cretaceous period, about 100 to 94 million years ago. The genus was known first from ...
''. In the 2012 description of ''
Ichthyovenator ''Ichthyovenator'' is a genus of spinosaurid dinosaur that lived in what is now Laos, sometime between 120 and 113 million years ago, during the Aptian Stage (geology), stage of the Early Cretaceous Period (geologic time), period. It is k ...
'', Allain et al. found it to belong to this subfamily, although almost all subsequent studies have found otherwise, placing it in
Spinosaurinae Spinosauridae (or spinosaurids) is a clade or family of tetanuran theropod dinosaurs comprising ten to seventeen known genera. Spinosaurid fossils have been recovered worldwide, including Africa, Europe, South America, and Asia. Their remains have ...
. Up until 2021, with ''
Cristatusaurus ''Cristatusaurus'' is a genus of theropod dinosaur that lived during the Early Cretaceous Geological period, Period of what is now Niger, 112 million years ago. It was a baryonychine member of the Spinosauridae, a group of large Bipedalism, bipe ...
'' and '' Suchosaurus'' being considered too incomplete and dubious, only the baryonychines ''Suchomimus'' and ''Baryonyx'' have been included in phylogenetic analyses, nearly always finding them to be sister genera in Baryonychinae, such as in the analysis performed by Arden et al. in 2018, shown below. In 2021, Chris Barker, Hone,
Darren Naish Darren William Naish (born 26 September 1975) is a British vertebrate palaeontologist, author and science communicator. As a researcher, he is best known for his work describing and reevaluating dinosaurs and other Mesozoic reptiles, including ...
, Andrea Cau, Lockwood, Foster, Clarkin, Schneider, and Gostling described two new spinosaurid species, ''Ceratosuchops inferodios'' and ''Riparovenator milnerae'', and placed them well-supportedly in Baryonychinae. They placed them within the newly created tribe Ceratosuchopsini alongside ''Suchomimus''. Barker et al. diagnosed three autapomorphies to distinguish the clade: ''"1. postorbital facet of frontal dorsoventrally thick (height more than 40% of length) and excavated by a deep, longitudinal slot; 2. well-defined and strongly curved anterior margins of supratemporal fossa; 3. occipital surface of the basisphenoid collateral oval scars excavated."'' Members of this clade range in length from 7.7 to 9.5 m (25.3 to 31 ft). The results of their Bayesian analysis appear below:


Paleobiology


Feeding

Baryonychine teeth are small and recurved with little to no serrations, resembling those of crocodiles. These are considered adaptations for piscivory, as numerous recurved teeth aid in holding a struggling slippery animal within the jaws and down the throat; rather than the serrated teeth in most other theropods which are generalized for cutting and ripping flesh. Vullo et al., 2016 likened the cranial evolution and adaptations to piscivory in spinosaurids to those of the
Muraenesocidae The Muraenesocidae, or pike congers, are a small family of marine eels found worldwide in tropical and subtropical seas. Some species are known to enter brackish water. Pike congers have cylindrical bodies, scaleless skin, narrow heads with larg ...
, a modern family of predatory eels with a similarly evolved skull. ''Baryonyx'' as one of the most complete representatives of the group shows evidence of a generalist behavior. One recorded instance is the holotype of ''Baryonyx'' found with both fish as well as a juvenile iguanodontid contents within the stomach region. Another instance is pointed out by a 2016 study by the Belgian palaeontologist Christophe Hendrickx and colleagues. They found that adult spinosaurs could displace their mandibular rami (halves of the lower jaw) sideways when the jaw was depressed, which allowed the pharynx (opening that connects the mouth to the oesophagus) to be widened. This jaw-articulation is similar to that seen in pterosaurs and living pelicans, and would likewise have allowed spinosaurids to swallow large prey such as fish and other animals. They also reported that the possible Portuguese '' Iberospinus'' (formerly seen as ''Baryonyx'') fossils were found associated with isolated ''Iguanodon'' teeth, and listed it along with other such associations as support for opportunistic feeding behaviour in spinosaurs.


References


External links

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