''Ampelognathus'' (meaning "grapevine jaw") is an extinct genus of possibly

rhabdodontomorph Rhabdodontomorpha is a clade of basal iguanodont dinosaurs. This group was named in 2016 in the context of the description, based on Spanish findings of an early member of the Rhabdodontidae. A cladistic analysis was conducted in which it was fou ...

ornithopod Ornithopoda () is a clade of ornithischian dinosaurs, called ornithopods (). They represent one of the most successful groups of herbivorous dinosaurs during the Cretaceous. The most primitive members of the group were bipedal and relatively sm ...

dinosaurs from 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 ...

(

Cenomanian The Cenomanian is, in the International Commission on Stratigraphy's (ICS) geological timescale, the oldest or earliest age (geology), age of the Late Cretaceous epoch (geology), Epoch or the lowest stage (stratigraphy), stage of the Upper Cretace ...

) Lewisville Formation of Texas. The type species is ''Ampelognathus coheni''.

Discovery and naming

The ''Ampelognathus''

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

, DMNH 2021-05-02, was found in sediments of the Lewisville Formation of the Woodbine Group (Arlington or Tarrant Member), dated to the Cenomanian age of the Late Cretaceous period, in the

Grapevine Lake Grapevine Lake is a reservoir in North Texas about northwest of Dallas and northeast of Fort Worth. It was impounded in 1952 by the U.S. Army Corps of Engineers when they dammed Denton Creek, a tributary of Trinity River. The reservoir's prim ...

emergency spillway of

Tarrant County Tarrant County is a county located in the U.S. state of Texas with a 2020 U.S. census population of 2,110,640, making it the third-most populous county in Texas and the 15th-most populous in the United States. Its county seat is Fort Worth. T ...

in Texas, United States. The specimen consists of a single, nearly-complete left

dentary In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone ...

. It was found away from the holotype of the

enantiornithean The Enantiornithes, also known as enantiornithines or enantiornitheans in literature, are a group of extinct avialans ("birds" in the broad sense), the most abundant and diverse group known from the Mesozoic era. Almost all retained teeth and cl ...

bird ''

Flexomornis ''Flexomornis'' (meaning "flexed shoulder bird") is a genus of enantiornithean birds known from fossils found in Texas rocks belonging to the Woodbine Formation (Lewisville Member) dating to the middle Cenomanian age of the late Cretaceous The ...

''. In 2023, Tykoski, Contreras & Noto described ''Ampelognathus coheni'' as a new genus and species of ornithopod dinosaur. The generic name, "''Ampelognathus''", combines the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

words "''ampelos''", meaning "grapevine", and "''gnathos''", meaning "jaw", in reference to the type locality in the emergency spillway of Grapevine Lake in Texas. The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

, "''coheni''", honors Murray Cohen, the discoverer of the holotype specimen.

Phylogeny

In their

phylogenetic analyses In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as Computational phylogenetics, phylogenetic inference. It infers the relationship among organ ...

, Tykoski, Contreras & Noto (2023) recovered ''Ampelognathus'' as a basal member of the Ornithopoda, as the

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

to the clade containing ''

Thescelosaurus ''Thescelosaurus'' ( ) is a genus of Ornithischia, ornithischian dinosaur that lived during the Late Cretaceous period (geology), period in western North America. It was named and described in 1913 by the Paleontology, paleontologist Charles W. G ...

'' and the

Iguanodontia Ornithopoda () is a clade of ornithischian dinosaurs, called ornithopods (). They represent one of the most successful groups of herbivorous dinosaurs during the Cretaceous. The most primitive members of the group were bipedal and relatively sm ...

. ''Ampelognathus'' was thus likely more closely related to iguanodontians than to the morphologically similar "

hypsilophodont Hypsilophodontidae (or Hypsilophodontia) is a traditionally used family of ornithopod dinosaurs, generally considered invalid today. It historically included many small bodied bipedal neornithischian taxa from around the world, and spanning from ...

s". The results of their phylogenetic analyses are shown in the

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

below: In 2024, Fonseca et al. comprehensively reanalyzed the interrelationships of early ornithischians, but were unable to include ''Ampelognathus'' in their phylogenetic analysis as the paper describing it was published after their data collection was completed. However, they commented on its relationships, stating that certain traits supported it as a member of

Rhabdodontomorpha Rhabdodontomorpha is a clade of basal iguanodont dinosaurs. This group was named in 2016 in the context of the description, based on Spanish findings of an early member of the Rhabdodontidae. A cladistic analysis was conducted in which it was f ...

, but a more basal member than either Tenontosauridae or Rhabdodontoidea. This position was subsequently supported in a 2025 publication by Czepiński & Madzia focused on rhabdodontomorphs, who included ''Ampelognathus'' in the phylogenetic dataset of Fonseca et al. (2024) and recovered results consistent with those postulated by the latter authors. These results are displayed in the cladogram below:

References

{{Taxonbar, from=Q123035115 Rhabdodontomorpha Dinosaur genera Cenomanian dinosaurs Dinosaurs of the United States Fossil taxa described in 2023