[1] 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.

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.

[1] 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.

[13][14] In 2023, Santos-Cubedo et al. described a new genus and species of baryonychine, Protathlitis cinctorrensis, based on a partial skeleton, recovered from the Arcillas de Morella Formation of Castellón, Spain.

[15] 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 of China dated to ~86-85 million years ago.

They interpreted the tooth as belonging to a probable baryonychine, which would expand the temporal range of Baryonychinae, and Megalosauroidea as a whole, well into the Late Cretaceous.

[10] Baryonychines possess reduced antorbital fenestrae in comparison to other theropods,[33] with most of the front snout being solid bone formed by the premaxillae and maxillae.

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.

[37] The clade was phylogenetically defined by Holtz et al. as all taxa more closely related to Baryonyx walkeri than to Spinosaurus aegyptiacus.

[13][39][40] Up until 2021, with Cristatusaurus 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.

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."

[42] Vullo et al, 2016 likened the cranial evolution and adaptations to piscivory in spinosaurids to those of the Muraenesocidae, a modern family of predatory eels with a similarly evolved skull.

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.