Aetodactylus, meaning “eagle finger”, was a pterosaur which lived in Texas during the middle Cretaceous Period 96 million years ago.
In 2006, workers at a construction site at Joe Pool Lake in Mansfield, Texas found a fossilized lower jaw from a pterosaur (collection ID code: SMU 76383) embedded within very fine-grained yellowish-brown calcareous sandstone. Also present were small fish vertebrae, a single fish tooth, and various unidentifiable bone fragments (Myers 2010, page 280). The rocks here belonged to the Tarrant Formation, which is found throughout north-central Texas. This was originally identified as a distinct geologic unit in 1932 by the geologist Walter S. Adkins. The type locality was listed as one mile east of Tarrant Station, Tarrant County, Texas close to a railroad bridge across a tributary of Bear Creek, and consisted of grey to greenish-brown sandy clay with intermittent thin bands of brownish limestone and calcareous concretions, the whole typically measuring 15 feet thick. The Tarrant Formation is overlain by the Britton Formation, which in turn is overlain by the Arcadia Park Formation. Altogether, these three formations make up the Eagle Ford Group. Fossils found within the Tarrant Formation include the ammonites Conlinoceras tarrantense (formerly Acanthoceras tarrantense), Eucalycoceras barcusi (formerly Acanthoceras barcusi), Euomphaloceras eulessanum, Exogyra columbella, Metengonoceras dumbli, and Tarrantoceras sellardsi. These ammonite fossils, which can be accurately dated, show that the Tarrant Formation dates to 96 MYA during the middle of the Cenomanian Stage of the middle Cretaceous Period (Adkins 1932, pages 240, 270, 424-425; Stephenson 1955, page 54; Cobban 1988, pages 5-7, 26; Andres and Myers 2013, pages 384, 394; Jacobs et al. 2013, page 6; “Conlinoceras tarrantense”). In addition to ammonite shells, isolated teeth attributed to the 15 foot long pliosaur Brachauchenius have also been found within the Tarrant Formation (Jacobs et al. 2013, page 6) as well as the marine lizard Coniasaurus cf. crassidens (Jacobs et al. 2013, page 7). According to Myers, “Deposition of the Eagle Ford Group recorded a north-northwestward transgression of Cretaceous seas along the Gulf Coast, followed by a highstand systems tract and local onset of regressive conditions due to continued progradation of deltaic complexes…In general, transgressive strata lower in the Eagle Ford Group represent low-energy, poorly oxygenated, deepwater environments” (Myers 2010, page 280).
In 2010, Timothy S. Myers officially named the pterosaur jawbone from Texas Aetodactylus halli, “Hall’s eagle finger”, named in honor of Lance Hall who found the specimen. Its official diagnosis was “subtle lateral expansion of anterior end of dentary; symphysis strongly compressed dorsoventrally; alveolar spacing relatively constant along mandible; mandibular rami dorsally inflected” (Myers 2010, page 280). The nearly-complete lower jaw measured 38.4 cm long; only the right side’s back tip and a small portion of the jaw’s underside were missing. The fusion of the left and right sides of the jaw, known as the “symphysis” (meaning “grow together”), measured 15.8 cm, or 41% of the jaw’s total length. Viewed from above, the jaw looks like a stretched-out wishbone. The front of the jaw is expanded slightly laterally, and the whole jaw itself has a slight concave curvature. Perhaps the most remarkable thing about the jaw is how flat it is. This might be accounted for by crushing under thousands of tons of rocks – many fossils are crushed as flat as a pancake – but Tim Myers posited that the jaw would have been very thin and flat even in life. The lower jaw had 54 tooth sockets, with 27 on each side. The largest tooth sockets are along the length of the symphysis, but when the left and right sides separate from each other, the tooth sockets get progressively smaller the further you go towards the back of the jaw. No teeth are preserved except for a very small replacement tooth embedded within the jaw located in the eighth left socket and the broken-off bottom end of another tooth in the twelfth right socket. These two teeth show that they were oval in cross-section and slightly recurved. Curiously, there are small indentations located along the rear half of the jaw’s left and right sides in between the tooth sockets. Tim Myers hypothesized that these were “occlusal pits” – places where the teeth in the missing upper jaw rubbed against the bone – which, if true, meant that the teeth were not splayed outwards but were arranged nearly vertically (Myers 2010, pages 280-287).
Aetodactylus was originally referred to the pterosaur family Ornithocheiridae, and Tim Myers particularly noted its similarity to Coloborhynchus with relation to the size and shape of the tooth sockets and also to Boreopterus (Myers 2010, pages 280-287). However three years afterwards, Brian Andres and Timothy Myers stated that Aetodactylus was actually a member of the superfamily Pteranodontoidea basal to the family Ornithocheiridae (Andres and Myers 2013, pages 388, 394). In 2015, phylogenic analyses showed that Aetodactylus was a member of a new pterosaur group which was christened Targaryendraconia, named in honor of the dragon-flying Targaryen family from Game of Thrones. This clade was divided into the family Cimoliopteridae which included Aetodactylus, Camposipterus, and Cimoliopterus, and the family Targaryendraconidae which included Aussiedraco, Barbosania, and the eponymous Targaryendraco (Myers 2015, pages 6-7; Pêgas et al. 2019, pages 2-3, 8).
Determining the overall size of Aetodactylus is difficult because we only have the lower jaw. However, Tim Myers noted this fossil’s overall similarity to the jaw of Boreopterus from the early Cretaceous Yixian Formation of northeastern China. Boreopterus had a skull measuring 23 cm (9 inches) and an overall wingspan of 150 cm (4.9 feet) (“Boreopterus”). If we scale Aetodactylus’ jaw to these proportions, then this means that Aetodactylus could have had a wingspan of 250.4 cm (98.6 inches / 8.2 feet). However, until we find a complete skeleton, this is just a hypothetical estimate.
Aetodactylus seems to have borne a striking outward appearance towards another group of pterosaurs called the ctenochasmatids, meaning “comb jaws”. This was a group of pterosaurs which existed from the late Jurassic to middle Cretaceous Periods which had long thin jaws packed with numerous long needle-like teeth perfect for snapping up fish. Examples include Ctenochasma itself, Gnathosaurus, Kepodactylus, and Pterodaustro. However, despite Aetodactylus’ outward visual similarity to the ctenochasmatids, Tim Myers noted that closer examination of its jaw proved that this was not the case, as ctenochasmatids usually had a multitude of tiny tooth sockets packed close together, especially at the front of their jaws, while Aetodactylus’ tooth sockets are fewer, larger, and are spread further apart. Ctenochasmatid teeth are also typically circular in cross-section, while Aetodactylus’ tooth sockets are oval and positioned diagonally (Myers 2010, pages 282-3).
There is no evidence for a crest extending out of the bottom of Aetodactylus’ lower jaw, as is seen in some pterosaurs like Anhanguera and Tropeognathus (Myers 2010, page 281). However, due to Aetodactylus’ close relationship to Cimoliopterus, which is known to have a short crest on top of its upper jaw, Aetodactylus might have also had this feature. Even so, at the moment, this is purely hypothetical.
Aetodactylus halli. © Jason R. Abdale (December 2, 2025).
I truly enjoy writing my articles and drawing my art, but it’s increasingly clear that I can’t keep this up without your gracious financial assistance. Kindly check out my pages on Redbubble and Fine Art America if you want to purchase merch of my artwork. Consider buying my ancient Roman history books Four Days in September: The Battle of Teutoburg and The Great Illyrian Revolt if you or someone that you know loves that topic, or my ancient Egyptian novel Servant of a Living God if you enjoy action and adventure. Please consider becoming a patron on my Patreon page so that I can continue to purchase the art supplies and research materials that I need. Professional art supplies are pricey, many research articles are “pay to read”, and some academic journals are rather expensive. My Patreon membership is just $1 per month – that’s it. If everybody who likes this drawing donates just one dollar per month, it would go a long way to keeping my blog “Dinosaurs and Barbarians” running and preventing my career in paleo-art from going extinct.
Keep your pencils sharp, everybody.
Bibliography
Articles
Adkins, W. S. (1932). “The Mesozoic Systems in Texas”. In Sellards, E. H.; Adkins, W. S.; Plummer, F. B., eds. The Geology of Texas. Volume I: Stratigraphy. The University of Texas Bulletin, number 3232 (August 22, 1932). Austin: The University of Texas at Austin, 1932. Pages 239-518.
https://store.beg.utexas.edu/publications/ut-bulletin/bl3232.
Andres, Brian; Myers, Timothy S. (2013). “Lone Star Pterosaurs”. Earth and Environmental Science Transactions of the Royal Society of Edinburgh, volume 103, issue 3-4 (2013). Pages 383-398.
https://www.researchgate.net/publication/259437218_Lone_Star_Pterosaurs.
Cobban, William A. (1988). “Tarrantoceras Stephenson and related ammonoid genera from Cenomanian (Upper Cretaceous) rocks in Texas and the Western Interior of the United States”. U.S. Geological Survey Professional Paper 1473. Washington, D.C.: United States Government Printing Office, 1988. Pages 1-51.
https://pubs.usgs.gov/pp/1473/report.pdf.
Jacobs, Louis L.; Polcyn, Michael J.; Winkler, Dale A.; Myers, Timothy S.; Kennedy, Jamell G.; Wagner, John B. (2013). “Late Cretaceous Strata and Vertebrate Fossils of North Texas”. In Hunt, B. B.; Catlos, E. J., eds. The Geological Society of America, Field Guide 30: Late Cretaceous to Quaternary Strata and Fossils of Texas – Field Excursions Celebrating 125 Years of GSA and Texas Geology. GSA South-Central Section Meeting, Austin, Texas, April 2013 (2013). Pages 1-13.
https://www.academia.edu/4673372/Late_Cretaceous_strata_and_vertebrate_fossils_of_North_Texas.
Myers, Timothy S. (2010). “A new ornithocheirid pterosaur from the Upper Cretaceous (Cenomanian-Turonian) Eagle Ford Group of Texas”. Journal of Vertebrate Paleontology, volume 30, issue 1 (January 2010). Pages 280-287.
https://www.researchgate.net/publication/232686212_A_new_ornithocheirid_pterosaur_from_the_Upper_Cretaceous_Cenomanian-Turonian_Eagle_Ford_Group_of_Texas.
Myers, Timothy S. (2015). “First North American occurrence of the toothed pteranodontoid pterosaur Cimoliopterus”. Journal of Vertebrate Paleontology, volume 35, issue 6: e1014904.
https://www.researchgate.net/publication/283490473_First_North_American_occurrence_of_the_toothed_pteranodontoid_pterosaur_Cimoliopterus.
Pêgas, Rodrigo V.; Holgado, Borja; Leal, Maria Eduarda C. (2019). “On Targaryendraco wiedenrothi gen. nov. (Pterodactyloidea, Pteranodontoidea, Lanceodontia) and recognition of a new cosmopolitan lineage of Cretaceous toothed pterodactyloids”. Historical Biology, volume 33, issue 4 (November 2019). Pages 1-15.
https://www.researchgate.net/publication/337363603_On_Targaryendraco_wiedenrothi_gen_nov_Pterodactyloidea_Pteranodontoidea_Lanceodontia_and_recognition_of_a_new_cosmopolitan_lineage_of_Cretaceous_toothed_pterodactyloids.
Stephenson, Lloyd William (1955). “Basal Eagle Ford Fauna (Cenomanian) in Johnson and Tarrant Counties, Texas”. Geological Survey Professional Paper 274-C. Washington, D.C.: United States Government Printing Office, 1955. Pages 53-65.
https://www.google.com/books/edition/Geological_Survey_Professional_Paper/Y0IRAAAAIAAJ?hl=en&gbpv=1.
Websites
Mindat. “Conlinoceras tarrantense”.
https://www.mindat.org/taxon-8650679.html. Accessed on November 25, 2025.
Pteros. “Boreopterus”.
https://www.pteros.com/pterosaurs/boreopterus.html. Accessed on November 30, 2025.
Categories: Paleontology, Uncategorized
DINOSAURS AND BARBARIANS 
Leave a comment