[D] Oryctodromeus cubicularis [sG] [T]
Describer
Varricchio, Martin and Katsura 2007
Time
Cretaceous Late Cenomanian
Classification
Ornithischia Ornithopoda Euornithpoda
Diet
Herbivore
Fossilsite
Blackleaf Formation near the Lima Peaks, Beaverhead Co., Montana, US
Info
Genus - Typespecies
Oryctodromeus has yielded the first trace and body fossil evidence of burrowing behaviour in a dinosaur. Skeletal remains of an adult and two juveniles of Oryctodromeus cubicularis gen. et sp. nov., a new species of hypsilophodont-grade dinosaur, were found in the expanded distal chamber of a sediment-filled burrow. Correspondence between burrow and adult dimensions supports Oryctodromeus as the burrow maker.
Additionally, Oryctodromeus exhibits features of the snout, shoulder girdle and pelvis consistent with digging habits while retaining cursorial hindlimb proportions. Association of adult and young within a terminal chamber provides definitive evidence of extensive parental care in the Dinosauria.
As with modern vertebrate cursors that dig, Burrowing in Oryctodromeus may have been an important adaptation for the rearing of young. Burrowing also represents a mechanism by which small dinosaurs may have exploited the extreme environments of polar latitudes, deserts and high mountain areas. The ability among dinosaurs to find or make shelter may contradict some scenarios of the Cretaceous–Paleogene impact event. Burrowing habits expand the known range of nonavian dinosaur behaviours and suggest that the cursorial ancestry of dinosaurs did not fully preclude the evolution of different functional regimes, such as fossoriality.
Holotype
MOR 1636a consists of the following elements: fused premaxillae; posterior/occipital region of the braincase; three cervical, six dorsal, sacrum and 23 caudal vertebrae; three dorsal ribs; scapulocoracoid; scapula; coracoid; humerus; ulna; radius; tibiae; distal fibula; and metatarsal IV.
Paratype
MOR 1636b includes cranial and postcranial materials found in association with the holotype and represents two juveniles with most linear dimensions measuring 55% to 65% those of the adult
Etymology
The generic name comes from the Greek words orycto and dromeus, meaning the ‘digging runner’. The species name, cubicularis, translates to ‘of the lair’, referring to the inferred denning habit of the taxon.
Description
Medium-sized, hypsilophodont-grade, basal ornithopod; adult humerus length 157 mm and adult tibia 254 mm. Extensive adult fusion (premaxillae, posterior braincase, all neurocentrum sutures, sacrum and scapulocoracoid). Anterior margin and posterior nasal processes of premaxillae angled more posterodorsally (at 458) than in Zephyrosaurus (Sues 1980). Juvenile lacking jugal boss; adult condition unknown. Cervical centra weakly opisthocoelous.
Transverse processes of anterior dorsal vertebrae steeply angled. Parapophysis and diapophysis not occurring together on horizontal plane until possibly dorsal six or seven, as in more advanced ornithopods such as Tenontosaurus and Iguanodon (Scheetz, 1999). Sacral ribs forming continuous iliac contact surface from the pubic peduncle through length of brevis shelf. Third sacral vertebra with small abutment for bracing of pubis.
Caudal centra developing more hexagonal cross-sections distally with transverse processes diminishing rapidly and absent by 20th caudal. Post-zygopophyses by about caudal-14 consisting simply of lateral depressions at the neural spine base. In more distal caudal vertebrae, elongate pre-zygopophyses simply overlap the shortening neural spine.
Few ossified tendons and absence of a tendon lattice in tail. Robust scapula longer than humerus (176 versus 157 mm) and with long, narrow acromion running nearly perpendicular away from scapular blade. As in other hypsilophodonts (Norman et al. 2004), ilium with bulbous antitrochanter (supracetabular process) on ischial peduncle.
Bone completely encircling obturator foramen. Bowed femur with pendant fourth trochanter and small cleft separating the cranial and greater trochanters. Juvenile hindlimb ratios of 1.19 for tibia/femur and 0.58 for metatarsal III/femur, adult ratios probably similar but slightly lower.
Varricchio, Martin and Katsura 2007
Time
Cretaceous Late Cenomanian
Classification
Ornithischia Ornithopoda Euornithpoda
Diet
Herbivore
Fossilsite
Blackleaf Formation near the Lima Peaks, Beaverhead Co., Montana, US
Info
Genus - Typespecies
Oryctodromeus has yielded the first trace and body fossil evidence of burrowing behaviour in a dinosaur. Skeletal remains of an adult and two juveniles of Oryctodromeus cubicularis gen. et sp. nov., a new species of hypsilophodont-grade dinosaur, were found in the expanded distal chamber of a sediment-filled burrow. Correspondence between burrow and adult dimensions supports Oryctodromeus as the burrow maker.
Additionally, Oryctodromeus exhibits features of the snout, shoulder girdle and pelvis consistent with digging habits while retaining cursorial hindlimb proportions. Association of adult and young within a terminal chamber provides definitive evidence of extensive parental care in the Dinosauria.
As with modern vertebrate cursors that dig, Burrowing in Oryctodromeus may have been an important adaptation for the rearing of young. Burrowing also represents a mechanism by which small dinosaurs may have exploited the extreme environments of polar latitudes, deserts and high mountain areas. The ability among dinosaurs to find or make shelter may contradict some scenarios of the Cretaceous–Paleogene impact event. Burrowing habits expand the known range of nonavian dinosaur behaviours and suggest that the cursorial ancestry of dinosaurs did not fully preclude the evolution of different functional regimes, such as fossoriality.
Holotype
MOR 1636a consists of the following elements: fused premaxillae; posterior/occipital region of the braincase; three cervical, six dorsal, sacrum and 23 caudal vertebrae; three dorsal ribs; scapulocoracoid; scapula; coracoid; humerus; ulna; radius; tibiae; distal fibula; and metatarsal IV.
Paratype
MOR 1636b includes cranial and postcranial materials found in association with the holotype and represents two juveniles with most linear dimensions measuring 55% to 65% those of the adult
Etymology
The generic name comes from the Greek words orycto and dromeus, meaning the ‘digging runner’. The species name, cubicularis, translates to ‘of the lair’, referring to the inferred denning habit of the taxon.
Description
Medium-sized, hypsilophodont-grade, basal ornithopod; adult humerus length 157 mm and adult tibia 254 mm. Extensive adult fusion (premaxillae, posterior braincase, all neurocentrum sutures, sacrum and scapulocoracoid). Anterior margin and posterior nasal processes of premaxillae angled more posterodorsally (at 458) than in Zephyrosaurus (Sues 1980). Juvenile lacking jugal boss; adult condition unknown. Cervical centra weakly opisthocoelous.
Transverse processes of anterior dorsal vertebrae steeply angled. Parapophysis and diapophysis not occurring together on horizontal plane until possibly dorsal six or seven, as in more advanced ornithopods such as Tenontosaurus and Iguanodon (Scheetz, 1999). Sacral ribs forming continuous iliac contact surface from the pubic peduncle through length of brevis shelf. Third sacral vertebra with small abutment for bracing of pubis.
Caudal centra developing more hexagonal cross-sections distally with transverse processes diminishing rapidly and absent by 20th caudal. Post-zygopophyses by about caudal-14 consisting simply of lateral depressions at the neural spine base. In more distal caudal vertebrae, elongate pre-zygopophyses simply overlap the shortening neural spine.
Few ossified tendons and absence of a tendon lattice in tail. Robust scapula longer than humerus (176 versus 157 mm) and with long, narrow acromion running nearly perpendicular away from scapular blade. As in other hypsilophodonts (Norman et al. 2004), ilium with bulbous antitrochanter (supracetabular process) on ischial peduncle.
Bone completely encircling obturator foramen. Bowed femur with pendant fourth trochanter and small cleft separating the cranial and greater trochanters. Juvenile hindlimb ratios of 1.19 for tibia/femur and 0.58 for metatarsal III/femur, adult ratios probably similar but slightly lower.