Papers by Markus J Martin
Geological Magazine
Horseshoe crabs as a group are renowned for their morphological conservatism punctuated by marked... more Horseshoe crabs as a group are renowned for their morphological conservatism punctuated by marked shifts in morphology associated with the occupation of non-marine environments and have been suggested to exhibit a consistent developmental trajectory throughout their evolutionary history. Here, we report a new species of horseshoe crab from the Ordovician (Late Sandbian) of Kingston, Ontario, Canada, from juvenile and adult material. This new species provides critical insight into the ontogeny and morphology of the earliest horseshoe crabs, indicating that at least some Palaeozoic forms had freely articulating tergites anterior to the fused thoracetron and an opisthosoma comprising 13 segments.
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Journal of Paleontology, 2019
Rhenopyrgids are rare, turreted edrioasterid edrioasteroids from the lower Paleozoic with a disti... more Rhenopyrgids are rare, turreted edrioasterid edrioasteroids from the lower Paleozoic with a distinctive and apparently conservative morphology. However, new, well-preserved rhenopyrgid edrioasteroid material from Canada, along with a review of described taxa, has revealed broader structural diversity in the oral surface and enabled a re-evaluation of rhenopyrgid functional morphology and paleoecology.The floor plates inRhenopyrgus vivianin. sp.,R.coronaeformisRievers, 1961 and,R.flosKlug et al., 2008 are well fused to each other and the interradial oral plate and lack obvious sutures, thereby forming a single compound interradial plate. This differs from other rhenopyrgids where sutures are more apparent. Such fused oral surface construction is only otherwise seen in some derived edrioblastoids and in the cyathocystids, suggesting homoplasy.Our analysis further suggests that the suboral constriction could contract but the flexible pyrgate zone could not. Thus, specimens apparently l...
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Geology, 2017
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Geology, 2009
Abstract Pyritization of soft tissues is extremely rare. Pyritized fossils have been discovered a... more Abstract Pyritization of soft tissues is extremely rare. Pyritized fossils have been discovered at six new localities spanning 54 km of outcrop of the Ordovician Lorraine Group of New York State, suggesting that soft-tissue pyritization is widespread in the Taconic basin. Notable new taxa with soft-tissue preservation include ostracods and other arthropods. Such fossils are rare and occur within 4–9-cm-thick mudstones representing single rapid depositional events. High ratios of reactive iron to total iron and high values of δ 34 S, ...
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Current Biology, 2014
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Geology, 2013
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New rhenopyrgid edrioasteroids (Echinodermata) and their implications for taxonomy, functional morphology, and paleoecology, 2019
Rhenopyrgids are rare, turreted edrioasterid edrioasteroids from the lower Paleozoic with a disti... more Rhenopyrgids are rare, turreted edrioasterid edrioasteroids from the lower Paleozoic with a distinctive and apparently conservative morphology. However, new, well-preserved rhenopyrgid edrioasteroid material from Canada, along with a review of described taxa, has revealed broader structural diversity in the oral surface and enabled a re-evaluation of rhenopyrgid functional morphology and paleoecology. The floor plates in Rhenopyrgus viviani n. sp., R. coronaeformis Rievers, 1961 and, R. flos Klug et al., 2008 are well fused to each other and the interradial oral plate and lack obvious sutures, thereby forming a single compound interradial plate. This differs from other rhenopyrgids where sutures are more apparent. Such fused oral surface construction is only otherwise seen in some derived edrioblastoids and in the cyathocystids, suggesting homoplasy. Our analysis further suggests that the suboral constriction could contract but the flexible pyrgate zone could not. Thus, specimens apparently lacking a sub-oral constriction should not necessarily be placed in separate genera within the Rhenopyrgidae. It also supports rhenopyrgids as epifaunal mud-stickers with only the bulbous, textured, entire holdfasts (coriaceous sacs) anchored within the substrate rather than as burrow dwellers or encrusters. Rhenopyrgus viviani n. sp. is described from the Telychian (lower Silurian) Jupiter Formation of Anticosti Island, Québec, Canada and is differentiated by a high degree of morphological variability of pedunculate plates, broader oral plates, and narrower distal ambulacral zones. Specimens lacking or with obscured diagnostic plates from the Ordovician of Montagne Noire, France, and the Ordovician and Silurian of Girvan, Scotland are also described. UUID: http://zoobank.org/7f81d67f-4155-4719-8a45-b278ad70739d
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Geology, 2009
Abstract Pyritization of soft tissues is extremely rare. Pyritized fossils have been discovered a... more Abstract Pyritization of soft tissues is extremely rare. Pyritized fossils have been discovered at six new localities spanning 54 km of outcrop of the Ordovician Lorraine Group of New York State, suggesting that soft-tissue pyritization is widespread in the Taconic basin. Notable new taxa with soft-tissue preservation include ostracods and other arthropods. Such fossils are rare and occur within 4–9-cm-thick mudstones representing single rapid depositional events. High ratios of reactive iron to total iron and high values of δ 34 S, ...
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Current Biology, 2014
Ostracod crustaceans are the most abundant fossil arthropods and are characterized by a long stra... more Ostracod crustaceans are the most abundant fossil arthropods and are characterized by a long stratigraphic range. However, their soft parts are very rarely preserved, and the presence of ostracods in rocks older than the Silurian period [1-5] was hitherto based on the occurrence of their supposed shells. Pyritized ostracods that preserve limbs and in situ embryos, including an egg within an ovary and possible hatched individuals, are here described from rocks of the Upper Ordovician Katian Stage Lorraine Group of New York State, including examples from the famous Beecher's Trilobite Bed [6, 7]. This discovery extends our knowledge of the paleobiology of ostracods by some 25 million years and provides the first unequivocal demonstration of ostracods in the Ordovician period, including the oldest known myodocope, Luprisca incuba gen. et sp. nov. It also provides conclusive evidence of a developmental brood-care strategy conserved within Ostracoda for at least 450 million years.
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Despite a plethora of exceptionally preserved trilobites, trilobite reproduction has remained a m... more Despite a plethora of exceptionally preserved trilobites, trilobite reproduction has remained a mystery. No previously described trilobite has unambiguous eggs or genitalia preserved. This study reports the first occurrence of in situ preserved eggs belonging to Triarthrus eatoni (Hall, 1838) trilobites from the Lorraine Group in upstate New York, USA. Like other exceptionally preserved trilobites from the Lorraine Group, the complete exoskeletons are replaced with pyrite. The eggs are spherical to elliptical in shape, nearly 200 µm in size, and are clustered in the genal area of the cephalon. The fact that the eggs are smaller than the earliest-known trilobite ontogenetic (protaspis) stage suggests that trilobites may have had an unmineralized preliminary stage in their ontogeny, and that the protaspis shield formed only after hatching. The eggs are only visible ventrally with no dorsal brood pouch or recognized sexual dimorphism. The location of the eggs is consistent with where modern female horseshoe crabs release their unfertilized eggs from the ovarian network within their head. Trilobites likely released their gametes (eggs and sperm) through a genital pore of as-yet unknown location (likely near the posterior boundary of the head). If the T. eatoni reproductive biology is representative of other trilobites, they spawned with external fertilization, possibly the ancestral mode of reproduction for early arthropods. Because pyritization preferentially preserves the external rather than internal features of fossils, it is suggested that there is likely a bias in the fossil record toward the preservation of arthropods that brood eggs externally: arthropods that brood their eggs internally are unlikely to preserve any evidence of their mode of reproduction.
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Papers by Markus J Martin