Multi-proxy dentition analyses reveal niche partitioning between sympatric herbivorous dinosaurs

Abstract

Dentitions of the sympatric herbivorous dinosaurs Hungarosaurus (Ankylosauria, Nodosauridae) and Mochlodon (Ornithopoda, Rhabdodontidae) (Santonian, Hungary) were analysed to investigate their dietary ecology, using several complementary methods—orientation patch count, tooth replacement rate, macrowear, tooth wear rate, traditional microwear, and dental microwear texture analysis (DMTA). Tooth formation time is similar in Hungarosaurus and Mochlodon, and traditional and DMTA microwear features suggest low-browsing habits for both taxa, consistent with their inferred stances and body sizes. However, Mochlodon possesses a novel adaptation for increasing dental durability: the dentine on the working side of the crown is double the thickness of that on the balancing side. Moreover, crown morphology, enamel thickness, macrowear orientation, and wear rate differ greatly between the two taxa. Consequently, these sympatric herbivores probably exploited plants of different toughness, implying dietary selectivity and niche partitioning. Hungarosaurus is inferred to have eaten softer vegetation, whereas Mochlodon likely fed on tougher material. Compared to the much heavier, quadrupedal Hungarosaurus, the bipedal Mochlodon wore down more than twice as much of its crown volume during the functional life of the tooth. This heavy tooth wear might correlate with more intensive food processing and, in turn, could reflect differences in the metabolic requirements of these animals.

Tooth replacement in the early-diverging neornithischian Jeholosaurus shangyuanensis and implications for dental evolution and herbivorous adaptation in Ornithischia

“…In the mesiodistal thin-section of rPM5 in the early juvenile CUGW VH132, the tooth formation time is 25 days in the premaxilla (Table 3). This duration is lower than Hungarosaurus (63–126 days), Mochlodon (77–140 days), Pinacosaurus (75 days), Edmontonia (279 days), and Changchunsaurus (58 days) [ 52 , 53 ]. In Triceratops and hadrosaurs, the mean tooth formation times range from 132 to 381 days [ 36 ].…”

“…The difference in tooth replacement rate is caused mainly by size differences in view of the similar DDAR. For comparison, the tooth replacement rate is faster than Mochlodon (140 days), Triceratops (83 days), hadrosaurs (range from 46 to 83 days), and ankylosaurs (53–120 days) [ 36 , 53 ]. The tooth replacement rate in Jeholosaurus is similar to those sauropods with dental batteries [ 54 ].…”

An early-diverging iguanodontian (Dinosauria: Rhabdodontomorpha) from the Late Cretaceous of North America

“…Quantitative and descriptive studies of rhabdodontid dietary ecology suggest these ornithischians were specialized, high-fiber herbivores that occupied dietary niches distinct from those of hadrosauromorphs and nodosaurids [ 111 ], with possible overlap among early ceratopsians [ 108 ]. However, to date, our understanding of ornithischian niche partitioning and sympatry in rhabdodontomorph-bearing assemblages is limited, stemming predominantly from the mosaic Late Cretaceous record of the European archipelago, with inconsistently resolved taxa from Australia and North America.…”

The coevolution of rostral keratin and tooth distribution in dinosaurs

“…Many avian traits, such as feathers, genomic contraction and hollow bones, were also thought to be adaptations for flight, but research in the last four decades has revealed other functional contexts [6][7][8][9][10][11][12][13].Mesozoic dinosaurs were tremendously successful-they occupied a diverse range of ecological niches comparable to modern mammals [14,15]. Niche partitioning among sympatric dinosaurs can be inferred by differences in tooth shape, deposition of dentin, tooth replacement rates and jaw mechanics [16]. However, unlike mammals, several dinosaur groups evolved keratinous beaks;…”

“…Mesozoic dinosaurs were tremendously successful-they occupied a diverse range of ecological niches comparable to modern mammals [14,15]. Niche partitioning among sympatric dinosaurs can be inferred by differences in tooth shape, deposition of dentin, tooth replacement rates and jaw mechanics [16]. However, unlike mammals, several dinosaur groups evolved keratinous beaks;…”