RICHARDS SPUR
The Richards Spur locality, which formed approximately 289 million years ago during the early Permian, is certainly a unique one, to say the least. All of the material comes from an active limestone quarry operated by the Dolese Brothers, who are kind enough to allow locals to come collect fossils that are found while mining. The locality is also quite unusual in the context of other early Permian deposits; whereas most localities represent floodplains and deltas, the Richards Spur locality is an upland ecosystem. Only two other upland localities from the early Permian are known: the nearby Bally Mountain site and the Bromacker site in Germany.
All of the animals were trapped in a unique cave (karst) system, which formed when older marine limestones were exposed at the surface and then weathered by water to form a network of mostly vertical tunnels. As a result of this natural trap, animals either fell in while they were alive or were washed in after they died, capturing a much wider range of animals than is typical of floodplain settings where the energetics of moving water lead to size-related sorting (smaller animals usually are often less common). Because many of the fossils weren't exposed to the elements or scavengers for very long and didn't experience the typical turbulence and damage associated with being carried down a river, the quality of preservation is exceptional and allows us to more readily identify details of these animals than is possible at other sites. To date, over 40 vertebrate taxa have been described, many by this lab, and some are only known from this single site. Most of these taxa were also terrestrial and carnivorous, which also differs from other early Permian sites that tend to preserve a mixture of aquatic, semi-aquatic, and terrestrial forms, as well as some herbivores. Lastly, many of our animals are smaller than at other sites, which may be an accurate reflection of the ecological structure at Richards Spur, as we would expect to find the smaller elements of large animals (e.g., teeth) if they were there; as a result, many of the more characteristic early Permian animals such as Eryops, Dimetrodon, and Diadectes are virtually absent from the site. |
DENTAL HISTOLOGY
Although teeth are something that everyone is familiar with by virtue of going to the dentist, our teeth, and mammalian teeth in general, are only a small part of the broad picture of dental evolution among tetrapods. Not only can scientists study simple anatomical aspects such as a tooth's shape or the total tooth count, but we can also study aspects such as how the tooth is attached to the jaw, how often replacement teeth form and how they replace the existing teeth, and how teeth have changed across vertebrate groups over time. For example, many early tetrapods have simple conical teeth with a single point at the end and were fused to the jaw without much of a socket, whereas mammals such as humans have multiple types of teeth (e.g., canines, incisors), some of which have multiple cusps (molars) and that sit deep in a socket of the jaw without being fused to it.
The lab's interest in tooth histology technically dates back to Robert's lungfish years, but the past decade has seen an explosion in projects related to the development and evolutionary trends of teeth that started largely with the dissertations of former Ph.D. students Aaron LeBlanc and Kirstin Brink and the establishment of the histology lab at the Royal Ontario Museum (ROM). The abundance of material at Richards Spur naturally lends itself to histological sampling of the tetrapods from the site, but the lab has worked its way around the tree, ranging from studies on the dental batteries of hadrosaurids and captorhinids to the development of infolded dentine (plicidentine) in amniotes to the periodontal tissues associated with the modern mammalian dentition. |
Recent publications
- Maho, T., Maho, S., Scott, D., & Reisz, R.R. 2022. Permian hypercarnivore suggests dental complexity among early amniotes. Nature Communications, 13, 4882. doi.org/10.1038/s41467-022-32621-5
- Maho, T. & Reisz, R.R. 2022. Dental anatomy and replacement patterns in the early Permian stem amniote, Seymouria. Journal of Anatomy, 241(3), 628-634. doi.org/10.1111/joa.13715
- Chen, J., LeBlanc, A.R.H., Jin, L., Huang, T., and Reisz, R.R. 2018. Tooth development, histology, and enamel microstructure in Changchunsaurus parvus: Implications for dental evolution in ornithopod dinosaurs. PLoS ONE 13(11): e0205206. DOI: 10.1371/journal.pone.0205206
- Haridy, Y. 2018. Histological analysis of post-eruption tooth wear adaptations, and ontogenetic changes in tooth implantation in the acrodontan squamate Pogona vitticeps. PeerJ 6:e5923 DOI: 10.7717/peerj.5923
- LeBlanc, A.R.H., Brink, K.S., Whitney, M.R., Abdala, F., and Reisz, R.R. 2018. Dental ontogeny in extinct synapsids reveals a complex evolutionary history of the mammalian tooth attachment system. Proceedings of the Royal Society B, Biological Sciences 285(1890): 20181792. DOI: 10.1098/rspb.2018.1792
- Haridy, Y., LeBlanc, A.R.H. and Reisz, R.R., 2017. The Permian reptile Opisthodontosaurus carrolli: a model for acrodont tooth replacement and dental ontogeny. Journal of Anatomy, 232(3): 371-382. DOI: 10.1111/joa.12754
- Haridy, Y., MacDougall, M.J. and Reisz, R.R. 2017. The lower jaw of the Early Permian parareptile Delorhynchus, first evidence of multiple denticulate coronoids in a reptile. Zoological Journal of the Linnean Society, 0:00-00 (advance article). DOI: 10.1093/zoolinnean/zlx085
- Gee, B.M., Haridy, Y. and Reisz, R.R., 2017. Histological characterization of denticulate palatal plates in an Early Permian dissorophoid. PeerJ, 5: e3727. DOI: 10.7717/peerj.3727
- LeBlanc, A.R.H., Brink, K.S., Cullen, T.M. and Reisz, R.R., 2017. Evolutionary implications of tooth attachment versus tooth implantation: a case study using dinosaur, crocodilian, and mammal teeth. Journal of Vertebrate Paleontology, 37(5): e1354006. DOI: 10.1080/02724634.2017.1354006