[Paleontology • 2022] Paleolimulus mazonensis • On Paleolimulus from the Mazon Creek Konservat-Lagerstätte, Illinois

Paleolimulus mazonensis

Bicknell, Naugolnykh & McKenzie, 2022

DOI: 10.5852/cr-palevol2022v21a15

 twitter.com/RussellBicknel1

Horseshoe crabs are extant chelicerates with a fossil record extending back to the Ordovician. Despite the documentation of their long evolutionary history, xiphosurids are rarely preserved within fossil assemblages due to their unmineralized cuticular exoskeleton. However, in exceptional circumstances, an abundance of fossil xiphosurid specimens have been documented. The Moscovian-aged Mazon Creek Konservat-Lagerstätte represents one such fossil deposit with a high abundance and diversity of xiphosurids. Although fairly well known, the Paleolimulus specimens from the Mazon Creek have not yet been subject to a thorough taxonomic examination. In the light of recent efforts to organise Paleolimulus, we revisit this undescribed material, erect Paleolimulus mazonensis n. sp., and present a phylogenetic analysis that places P. mazonensis n. sp. as a sister taxon to P. signata (Beecher, 1904). The palaeoecology and possible ontogeny of P. mazonensis n. sp. are presented, as well as a statement on the future directions for understanding this xiphosurid genus.

KEYWORDS: Xiphosurida, horseshoe crabs, exceptional preservation, Paleozoic, Carboniferous, Paleolimulidae, new species

Paleolimulus mazonensis n. sp.

Russell D. C. Bicknell, Serge V. Naugolnykh and Scott C. McKenzie. 2022. On Paleolimulus from the Mazon Creek Konservat-Lagerstätte.  Comptes Rendus Palevol. 21(15); 303-322. DOI: 10.5852/cr-palevol2022v21a15

 sciencepress.mnhn.fr/en/periodiques/comptes-rendus-palevol/21/15

 twitter.com/RussellBicknel1/status/1519916175248879616

Sur Paleolimulus de la Konservat-Lagerstätte de Mazon Creek

Les xiphosuridés, aussi appelés limules, incluent des chélicérates actuels dont le registre fossile remonte à l'Ordovicien. Malgré les traces de leur longue histoire évolutive, les xiphosuridés sont rarement préservés dans les assemblages fossiles en raison de leur exosquelette cuticulaire non minéralisé. Cependant, dans des circonstances exceptionnelles, une abondance de spécimens de xiphosurides fossiles a été documentée. Le Konservat-Lagerstätte de Mazon Creek, d'âge Moscovien, représente un tel dépôt de fossiles qui présente une grande abondance et diversité de xiphosuridés. Bien que relativement bien connus, les spécimens de Paleolimulus de Mazon Creek n'ont pas encore fait l'objet d'un examen taxonomique approfondi. A la lumière des efforts récents pour organiser Paleolimulus, nous revisitons ce matériel non décrit, érigeons Paleolimulus mazonensis n. sp., et présentons une analyse phylogénétique qui place P. mazonensis n. sp. comme un taxon frère de P. signata (Beecher, 1904). La paléoécologie et l'ontogenèse possible de P. mazonensis n. sp. sont présentées, ainsi que des perspectives de recherches futures pour mieux comprendre ce genre xiphosuride fossile emblématique.

MOTS-CLÉS: Xiphosurida, les limules, préservation exceptionnelle, Paléozoïque, Carbonifère, Paleolimulidae, espèce nouvelle

[Paleontology • 2023] Archopterus anjiensis • The First Documentation of An Ordovician eurypterid (Chelicerata) from China

Archopterus anjiensis

Wang, Braddy, Botting & Zhang, 2023

 DOI: 10.1017/jpa.2023.21

Artwork: Dinghua Yang.

Abstract

An early form of eurypterids (Chelicerata), Archopterus anjiensis n. gen. n. sp., is described from the uppermost Ordovician Wenchang Formation of Anji County, Zhejiang Province, South China. It is the earliest record of eurypterids in China and likely the oldest representative of the Adelophthalmidae. The species, represented by a single specimen, is diagnosed by a ventrally preserved prosoma with a parabolic carapace, Hughmilleria-type prosomal appendages, a short vase-shaped metastoma, and a three-segmented type A (female) genital appendage. The specimen is preserved, together with diverse sponges, graptolites and occasional nautiloids, in a 10 m thick shale of marine deep-water setting. This finding extends the stratigraphic range of adelophthalmids from the previously recorded early Silurian into the Late Ordovician (some 10 million years older) and supports an earlier cryptic phase of eurypterid evolution in Gondwana.

Systematic paleontology

Subphylum Chelicerata Heymons, Reference Heymons1901

Order Eurypterida Burmeister, Reference Burmeister1843

Suborder Eurypterina Burmeister, Reference Burmeister1843

Family Adelophthalmidae Tollerton, Reference Tollerton1989

Genus Archopterus new genus

 

Etymology: Genus name from the Latin prefix arch-, meaning “ancient,” and -opterus, a common suffix for eurypterids, meaning “wing.”

Archopterus anjiensis n. gen. n. sp.

Holotype: NIGP 164906, Nanjing Institute of Geology and Palaeontology, CAS, China.

Diagnosis: Adelophthalmid with a parabolic carapace, Hughmilleria-type prosomal appendages, vase-shaped metastoma, and three-segmented type A (female) genital appendage.

Occurrence: Hirnantian (Metabolograptus persculptus Biozone) of the Wenchang Formation of Tianfucun, Anji County, Zhejiang Province, South China.

Etymology: The species is named after Anji County, where the type specimen was discovered.

 

Han Wang, Simon J. Braddy, Joseph Botting and Yuandong Zhang. 2023. The First Documentation of An Ordovician eurypterid (Chelicerata) from China. Journal of Paleontology. First View. DOI: 10.1017/jpa.2023.21