Athenar bermani

Athenar bermani is a dicraeosaurid sauropod dinosaur from the Uppermost Jurassic (Tithonian) Morrison Formation at Carnegie Quarry, Dinosaur National Monument, Utah, United States. Known exclusively from subadult holotype CM 26552 – a braincase and partial skull roof originally assigned to Diplodocus longus – this taxon was redescribed in 2025 as the fourth dicraeosaurid genus from the Morrison Formation. Its cranial anatomy, including unique fenestrae and a squamosal prong, aligns it closely with Suuwassea emilieae while distinguishing it from diplodocids, contributing to reevaluations of Late Jurassic sauropod diversity and biogeography in North America.

Etymology

The generic name Athenar honors the Cleveland musician and Pittsburgh Steelers fan Athenar, whose music accompanied much of the research on the specimen. The specific epithet bermani honors David S. Berman, who collaborated with John S. McIntosh on foundational studies of diplodocoid sauropod skulls at the Carnegie Museum of Natural History and co-authored the initial 1978 description of the holotype.

Physical Characteristics

Key diagnostic features from holotype CM 26552, a subadult braincase and partial skull roof with slight taphonomic distortion (transverse shearing shifting the right half dorsally).

• Length: 12–15 m (39–49 ft)*
• Weight: 5–10 t (11,023–22,046 lb)*

*The largest known specimen (subadult holotype; adult body length scaled from braincase width 89.9 mm vs. Suuwassea emilieae ~300–350 mm skull baseline, assuming 20–30% subadult growth and dicraeosaurid proportions per Harris and Dodson, 2004, and Whitlock et al., 2025; weight via volumetric scaling Mass ∝ L³ calibrated to Suuwassea 2–3 t at 7–8 m).

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The holotype of Athenar bermani, CM 26552, consists of a subadult braincase and partial skull roof with slight taphonomic distortion, including transverse shearing that shifts the right half dorsally.

Although known only from a braincase and partial skull roof, Athenar bermani reveals much about the anatomy and proportions of this Late Jurassic sauropod. The skull, compact and relatively low, suggests an animal with a short, deep head and a downward-facing snout, typical of dicraeosaurids – a group of smaller, more robust relatives of Diplodocus. The preserved occipital region measures about 8.9 cm (3.5 in) across, and the occipital condyle 4.5 × 3.1 cm (1.8 × 1.2 in), indicating a skull slightly smaller than that of Suuwassea emilieae but proportionally similar.

The braincase shows several diagnostic features: paired postparietal and frontoparietal openings, an expanded crista prootica, a distinct ventral prong on the squamosal, and a “tooth-like” projection at the junction of the parietal and opisthotic bones – an autapomorphy unique to Athenar. The wide supraoccipital crest implies strong neck muscle attachments, suggesting that the neck was held in a slightly elevated, forward-projecting posture rather than upright. The skull roof was ornamented with low ridges and rugose textures typical of flagellicaudatans, giving the head a reinforced, somewhat angular appearance.

Because only cranial remains are known, the overall body form must be inferred from close relatives. Dicraeosaurids were generally shorter and more compact than the long-necked Diplodocus, with proportionally shorter tails and sturdier necks. By scaling the preserved skull dimensions against those of Suuwassea, Kaatedocus, and Smitanosaurus, we estimate that Athenar bermani reached approximately 12–15 m (39–49 ft) in length and weighed between 5 and 10 t (11,000–22,000 lb). These estimates come from established allometric relationships between skull size and body mass in sauropods, but remain provisional until postcranial bones are discovered.

In life, Athenar was likely a powerfully built, medium-sized herbivore with a relatively short neck and compact body – traits that may have allowed greater agility and browsing at low to mid-level vegetation.

Diet and Feeding Habits

Herbivore; as a dicraeosaurid sauropod, likely browsed mid-level vegetation such as ferns (e.g., Cladophlebis), cycads (e.g., Otozamites), and conifers (e.g., Araucaria) using a moderately long neck, chisel-like teeth for cropping, and gastric grinding; inferred from clade-wide adaptations in Diplodocoidea.

Habitat and Distribution

North America, United States, Utah, Dinosaur National Monument, Morrison Formation (Uppermost Member, Quarry 13 horizon).

Paleoenvironment

Fluvial and floodplain deposits in a semi-arid seasonal climate with rivers, lakes, and wetlands; co-occurring taxa include theropods (Allosaurus fragilis, Ceratosaurus nasicornis), ornithischians (Stegosaurus stenops, Dryosaurus altus, Camptosaurus dispar), and sauropods (Diplodocus longus, Apatosaurus louisae, Barosaurus lentus, Camarasaurus supremus).

Behavior and Social Structure

Inferred from clade: gregarious herd-living for predator defense; neck potentially used in display or intra-specific combat via bifurcation or elongation (as in related Amargasaurus cazaui), though no direct evidence; subadult ontogeny suggests growth in social groups.

Discovery and Research

Holotype CM 26552 collected in 1913 by Earl Douglass from Carnegie Quarry (Quarry 13 horizon); undescribed until 1978 assignment to Diplodocus longus by Berman and McIntosh (basis for Diplodocus braincase description); redescribed and named Athenar bermani in 2025. No referred material. Phylogenetic analyses recover it within Dicraeosauridae (Flagellicaudata: Diplodocoidea), closely allied to Suuwassea emilieae via shared frontal contribution to supratemporal fenestra; distinguished from Kaatedocus siberi (lacks frontoparietal fenestra, frontal-supratemporal contact) and Smitanosaurus agilis (excludes frontal from supratemporal fenestra, narrower supraoccipital crest).

Discovery Context

Excavated from Tithonian fluvial sediments (~150–151 Ma) via stratigraphic correlation and U-Pb dating of ash beds; part of the prolific Carnegie Quarry bonebed preserving a diverse Morrison assemblage.

Significance and Interesting Facts

• Fourth dicraeosaurid genus from the Morrison Formation, increasing recognized North American diversity of the clade (previously limited to Suuwassea emilieae, Kaatedocus siberi, Smitanosaurus agilis).
• Reevaluation of 1978 Diplodocus assignment highlights impacts of new comparative data from South American (e.g., Amargasaurus cazaui, Bajadasaurus pronuspinax) and Asian (Lingwulong shenqi) dicraeosaurids on Morrison taxonomy.
• Shares potential synapomorphy (frontal-supratemporal fenestra contact) with Suuwassea emilieae, suggesting close phylogenetic ties despite debated temporal gap (Kimmeridgian vs. Tithonian).
• Holotype’s historical role in “recapitating” Apatosaurus and describing Diplodocus braincase underscores value of revisiting legacy specimens with modern methods.
• Naming integrates paleontology with music and sports culture (Athenar as musician/Steelers fan).
• Contributes to understanding diplodocoid cranial evolution, including fenestrae possibly linked to vascular or sensory functions.

Conclusion

Athenar bermani, through the redescription of CM 26552, reveals underestimated dicraeosaurid diversity in the Late Jurassic Morrison Formation, challenging prior diplodocid assignments and illuminating North American biogeographic patterns within Diplodocoidea. Its subadult cranial features – such as fenestrae, prongs, and nerve canal configurations – distinguish it from coeval taxa while aligning it closely with Suuwassea emilieae, potentially indicating a North American subclade. This discovery emphasizes the role of historical collections in advancing sauropod phylogenetics, with implications for global dispersal and evolutionary timelines of short-necked sauropods near the Jurassic-Cretaceous boundary.