| Eocarcharia | |
|---|---|
 | |
| Reconstructed skulls illustrating the chimaericEocarcharia hypodigm | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Family: | †Spinosauridae (?) |
| Subfamily: | †Baryonychinae (?) |
| Genus: | †Eocarcharia Sereno &Brusatte,2008 |
| Species: | †E. dinops |
| Binomial name | |
| †Eocarcharia dinops Sereno and Brusatte, 2008 | |
Eocarcharia (lit. 'dawn shark') is an extinctgenus oftheropod dinosaurs found in what is now the westernTénéré Desert of Niger. It is known from several skull bones collected in 2000 by an expedition to theEarly Cretaceous (Aptian–Albian ages)Elrhaz Formation (Gadoufaoua locality) led by American paleontologistPaul Sereno. The fossil material was then described in 2008 by Sereno andSteve Brusatte. The genus contains asingle species,Eocarcharia dinops. While Sereno and Brusatte identified all of the remains as belonging to a newcarcharodontosaurid, later studies suggested that the species is chimaeric, comprising bones of at least two unrelated taxa. Some of theEocarcharia material, including theholotype (name-bearing) specimen, likely belongs to abaryonychinespinosaurid. This would renderEocarcharia a member of this group, closely related to the coevalSuchomimus. Meanwhile, the definitively carcharodontosaurid bones, amaxilla and teeth, belong to a distinct unnamed taxon.
Little is known aboutEocarcharia due to its fragmentary and chimaeric nature. When considered a carcharodontosaurid, it was estimated to be 6–8 metres (20–26 ft) long, making it smaller thanderived carcharodontosaurids likeGiganotosaurus, andCarcharodontosaurus. Thepostorbital (bone behind the orbit) is robust with a large brow, a distinct characteristic ofEocarcharia. It was possibly covered inkeratin and used forhead-butting with other individuals of its species.Eocarcharia lived in an environment with rivers and vastfloodplains alongside many other dinosaurs,pterosaurs,crocodylomorphs, and freshwater animals.
In 2000, American paleontologistPaul Sereno led an expedition conducted with theUniversity of Chicago and funded by theNational Geographic Society. The purpose of this trip was to explore fossiliferoussandstone outcrops in a site on the western edge of the NigerianTénéré Desert known as Gadoufaoua.[1] These rock layers belong to theElrhaz Formation, dating to theEarly Cretaceous. During the expedition, several isolated theropod skull bones were collected, including amaxilla (main tooth-bearing bone of the upper jaw) and two maxilla fragments, fivepostorbitals (bone behind the orbit), twofrontals—one articulated with the leftprefrontal and one with a partialparietal (skull roof bones)—and fiveteeth. These remains were then transported to the University of Chicago forpreparation and study before being returned to theMusee National du Niger and deposited under the catalog numbers MNN GAD2–14.[2]
In 2008, Sereno andSteve Brusatte described all of these remains as belonging to a new genus and species of carcharodontosaurid dinosaur, namedEocarcharia dinops. They established one of the postorbitals, MNN-GAD2, as theholotype (name-bearing) specimen. Thegeneric name,Eocarcharia, derives from theAncient Greek wordseos, meaning'dawn', andkarcharias, meaning'shark', referencing the early-diverging nature ofEocarcharia in relation to its 'shark-toothed' relatives. Thespecific name,dinops, is a Greek term meaning'fierce-eyed', referring to the unique postorbital ornamentation above the eye.[2][3]
Based on the total fusion of the skull bones referred toEocarcharia, Sereno & Brusatte identified them as having come from fully mature adult individuals. Referencing the more complete skulls and skeletons of other carcharodontosaurids likeAcrocanthosaurus andCarcharodontosaurus, they determined thatEocarcharia was likely about 6–8 metres (20–26 ft) long, half the linear size of the largest, more derived members of the family.[2] Similar estimates were supported by later publications.[4][5]
.png)
.png)
The postorbital bears a thick, robustbrow that, likely due to its robustness, is well-preserved in multiple specimens. This brow is composed of two segments: ananterior (front) portion with boxy dimensions and aposterior (back) portion that forms an ovate orbital boss (large, thick bony mass). This orbital boss is positioned above the posterodorsal (top back) edge of theorbit, a trait noted by Sereno and Brusatte to bediagnostic (unique) to this species. However, exaggerated orbital bosses are also found inspinosaurids.[6][7]Mapusaurus andGiganotosaurus have orbital bosses as well, though these areossified as a distinct body from the rest of the postorbital. In contrast, the postorbital bosses ofCarcharodontosaurus andEocarcharia lack the extensive ossification seen inMapusaurus andGiganotosaurus.[2][8]
The margins of the postorbital make up segments of the orbit edges, thelaterotemporal fenestra, and thesupratemporal fenestra. Several of the postorbitals known fromEocarcharia preserve thearticular surfaces for thelacrimal, which are 9 millimetres (0.35 in) deep and 12 millimetres (0.47 in) long. These articular surfaces are very small and deep proportionally for a carcharodontosaurid, making this characteristic a diagnostic trait ofEocarcharia. In contrast, the point of contact between the postorbital and the frontal is rugose and bears a unique, plate-shapedprocess (projection of bone) that interlocks with a concavity on the frontal. Another diagnostic trait ofEocarcharia is that its postorbital bears a narrow facet which articulates laterally with thejugal (cheekbone), whereas carcharodontosaurids likeCarcharodontosaurus have broader facets.Midshafts of theventral (bottom) ramus (a branch of bone) of the postorbital in spinosaurids andmegalosaurids are typically U-shaped incross-section, whereas inEocarcharia it is subtriangular in cross-section. An infraorbital process is also present on the postorbital ventral ramus ofEocarcharia, distinct from those of other carcharodontosaurids in that it is small, rugose, anddistally-positioned (away from the body core).[2][7]
The frontal is known fromEocarcharia, and is proportionally very broad at its mid-length, similar to that ofCarcharodontosaurus. In dorsal view, the supratemporalfossa (a depression along thetemporal fenestra) is greatly exposed, another diagnostic characteristic. In ventral view, the anterior portion of the frontal is exposed, forming the roof of theolfactory section of theendocranium (the part of the skull that holds the brain). This portion of the frontal is narrow, in contrast to those oftetanurans, where it is typically broad. Notably, a prefrontal is also preserved. Independent prefrontals are absent in advanced carcharodontosaurids as they are typically co-ossified (fused) with thelacrimals into a single element,[9] whereas in earlier genera likeEocarcharia,Acrocanthosaurus, andConcavenator, they are unfused.[8] InEocarcharia, the prefrontal is relatively wide, about half the width of the frontal. The prefrontal bears an extended process that articulates with the deep, squared articular notch on the frontal. On the ventral (bottom) side of the frontal, theropods typically feature an extended process that travels along the posteromedial (back inner) portion of the bone.Eocarcharia lacks this process.[2]
.png)
One nearly complete maxilla and two central portions of the maxilla were initially referred toEocarcharia and definitively belong to a carcharodontosaurid or closely allied taxon.[7][10] The dentary has 15alveoli (tooth sockets). It is generally flat, which would have given this taxon a relatively narrow snout.Neurovascular foramina (small pits and grooves) cover the external surface. Theantorbital fossa, a depression on the side of the maxilla, is pierced by threefenestrae (holes), the largest of which is the subtriangular promaxillary fenestra, followed by the maxillary fenestra, which is subequal in size. A smaller round accessory fenestra is present above these two. Most of the alveoli in the complete maxilla preservereplacement teeth. Thetooth crowns are transversely compressed. Unlike many carcharodontosaurid teeth, those referred toEocarcharia are not blade-shaped and they lack straight posteriorcarina (cutting edges on the back of the crown) andenamel wrinkles with high relief.[2]
The phylogenetic position ofEocarcharia is complicated by the probable chimaeric nature of the specimens referred to it. All of the material was initially recognized as belonging to the same species, specifically an early-diverging carcharodontosaurid. While the maxilla and teeth clearly belong to a carcharodontosaurid or similar taxon, later research has suggested the holotype and skull roof may belong to an unrelated theropod, specifically a spinosaurid closely related toSuchomimus.[2][7]
In theirphylogenetic analyses—modified from a dataset published by the same authors later that year[11]—Sereno & Brusatte (2008) recognizedEocarcharia as anallosauroid theropod in an early-diverging position within the familyCarcharodontosauridae. They noted that the resolution of their trees was more stable withoutEocarcharia, since it could not be scored for most of the characters in their dataset. Regardless, their strict consensus tree recovered it as thesister taxon to the North AmericanAcrocanthosaurus.[2]
In the same 2008 paper, Sereno and Brusatte namedKryptops palaios based on anabelisaurid maxilla and postcranial remains. They assigned the postcranial material to the same individual as the maxilla based on their close association and alleged basal abelisaurid features in the vertebrae and pelvis.[2] In 2012, Matthew Carrano and colleagues consideredKryptops palaios to be achimera (specimen composed of multiple species), stating that its postcranial remains, especially the pelvis and sacrum, may belong to a carcharodontosaurid, possiblyEocarcharia. Since these bones do not overlap with theEocarcharia holotype, they could not be definitively referred to this taxon.[12] The hypothesis that these postcranial bones do not belong toKryptops was supported by later studies, which agreed that the remains belonged to a carcharodontosaurid[13][14] or ametriacanthosaurid.[7]
In their 2024 description of a new specimen of the giant carcharodontosauridTaurovenator, Rolando and colleagues includedEocarcharia in their phylogenetic analysis, recovering it as an early-diverging member of the clade, branching afterNeovenator. These results are displayed in thecladogram below:[15]
The skull bones ofEocarcharia belong to multiple individuals and were found in different sites. As such, the taxonomic identity of these bones—and whether or not they can all be referred to the same taxon—has been debated. In their description of the carcharodontosauridTameryraptor, Kellermann, Cuesta & Rauhut (2025) scored the holotype postorbital (including a referred frontal with articular surfaces that match those of the postorbital) and referred maxilla as separateoperational taxonomic units (OTUs) to test the likelihood that they belonged to the same taxon. In their analyses, both OTUs were consistently recovered in different positions, supporting their status as distinct taxa. The maxilla was reliably recovered as acarcharodontosauriform, either as a non-carcharodontosaurine carcharodontosaurid or as a metriacanthosaurid. On the other hand, the holotype was recovered in positions as a basal carcharodontosaur, or variably inside or outside of Carcharodontosauriformes. They interpreted these results as indicative of the referred maxilla skewing past analyses toward carcharodontosaur affinities for the taxon.[10]
In 2024,Andrea Cau published the results of a comprehensive theropod phylogenetic framework.[16] The following year, Cau and Alessandro Paterna used an updated version of this dataset to analyze the relationships of Cretaceous theropods from Africa, especially those known from multiple specimens with minimal overlapping material. The researchers scored two separate OTUs forEocarcharia: one for the referred maxilla and another comprising the skull roof material (including the holotype postorbital and referred frontal and prefrontal). As expected, the maxilla OTU was found to have close affinities with early-diverging carcharodontosaurids. More surprisingly, the holotype + skull roof OTU was recovered as the sister taxon to the coevalSuchomimus as abaryonychine within theSpinosauridae. These results were supported by the presence of at least seven traits shared byEocarcharia and spinosaurids that are absent in carcharodontosaurs. Cau and Paterna further recognized that two of theautapomorphies (unique derived traits) proposed forEocarcharia by Sereno and Brusatte are also uniquely shared withCeratosuchops, a baryonychine from theWessex Formation of the United Kingdom.[6] Furthermore, the prefrontal bone has a feature seen inBaryonyx but not allosauroids. Given the discrepancies with the placement ofEocarcharia as a carcharodontosaur and the many similarities toSuchomimus,Ceratosuchops, andRiparovenator, the researchers considered the genus to be most parsimoniously regarded as a spinosaurid.[7]
Cau and Paterna's phylogenetic results placedEocarcharia as the sister taxon toSuchomimus. Both species differ in fourteen characters, precluding their taxonomicsynonymization. This also provides further evidence for an observed trend of at least two spinosaurids coexisting in one ecosystem (e.g.,Ceratosuchops andRiparovenator in the Wessex Formation). Since the maxilla OTU was recovered as distinct from the holotype + skull roof OTU, Cau and Paterna suggested that this bone—which demonstrates apparent allosauroid anatomy consistent with carcharodontosaurids—should be referred to a new taxon. Abbreviated results of their phylogenetic analysis are displayed in the cladogram below, with bothEocarchia OTUs indicated: the skull roof and holotype within the spinosaurid cladeCeratosuchopsini and the maxilla as a basal carcharodontosaurid. ⊞ buttons can be clicked to expand nodes.[7]
| Carnosauria |
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Notably, spinosaurid similarities have been noted before Cau and Paterna's 2025 analysis; in 2022, Sereno and colleagues reported a newly-discovered skull roof specimen they assigned toSuchomimus.[17] The similarity of this specimen to the postorbital and frontal ofEocarcharia was noted by Schade and colleagues the following year.[18] In early 2025, Kellermann, Cuesta & Rauhut reinforced this comparison, claiming that theSuchomimus specimen may even belong toEocarcharia.[10] Cau and Paterna acknowledged these similarities, but noted characters more consistent withSuchomimus thanEocarcharia. They also commented on the possibility that some of the other specimens traditionally referred toSuchomimus may actually belong toEocarcharia.[7]
Due to the fragmentary, chimaeric, and indeterminate nature of the fossils ofEocarcharia, little can be directly known about itspaleobiology. In their 2008 description, Sereno and Brusatte noted the thickness and robustness of the postorbital bosses. The brow was likely covered inkeratin, extending its size. It also displays large, intricatesutures between the postorbital and frontal that suggest it would be stable against lateral impacts. The head of thelaterosphenoid is placed in a socket in the postorbital, which, although shallower than that of advanced carcharodontosaurids, would be able to handle stress. This combination of stress adaptations illustrates that the brow was for more than purely display purposes. This led the authors to hypothesize that the postorbital brows ofEocarcharia and carcharodontosaurids were used forintraspecific lateralhead-butting. While this brow is absent in allosauroids and most spinosaurids, the spinosauridsCeratosuchops andRiparovenator do preserve large orbital bosses comparable to those inEocarcharia.[6][7] Although present as general expansions in largetyrannosaurids, the postorbital bosses ofEocarcharia and carcharodontosaurids project laterally,[10][13] further suggesting that they played a role in lateral head-butting.[2]
Eocarcharia is known from theElrhaz Formation of theTegama Group in an area of the Nigerian Ténéré Desert called Gadoufaoua. The Elrhaz Formation consists mainly offluvial sandstones with low relief, much of which is obscured by sand dunes. Thesediments are coarse- to medium-grained, with almost no fine-grainedhorizons.[19]Eocarcharia lived about 120 to 112 million years ago, during theAptian toAlbian ages of the mid-Cretaceous.[2] It likely lived in habitats dominated by inlandfloodplains (ariparian zone).[20]
Eocarcharia lived alongside several other dinosaurs. These included other theropods, such as the spinosaurid and probable close relativeSuchomimus,Kryptops (known from a chimaeric combination ofabelisaurid andallosauroid material),[7] and the putativenoasauridAfromimus.[21] Severalmegaherbivores, including thehadrosauriformsOuranosaurus andLurdusaurus, thedryosauridElrhazosaurus, and twosauropods, therebbachisauridNigersaurus and an unnamedtitanosaur, have been unearthed from Gadoufaoua. Together, these comprise one of the few associations of megaherbivores with a balance of sauropods and largeornithopods.Crocodylomorphs includingAnatosuchus,Araripesuchus,Sarcosuchus, andStolokrosuchus were also found in these rock layers. In addition, remains of an unnamedornithocheiridpterosaur,turtles,bony fish, ahybodont (shark-like fish), andbivalves have been found. The aquatic fauna consists entirely of freshwater inhabitants.[20][22][23]
.jpg)
.jpg)
.png)
.jpg)
