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LXXXII.—A new eurypterid from the upper Old Red Sandstone of Portishead
... A number of other Drepanopterus species have been described however, although most have since been removed from the genus; 'D.' bembycoides Laurie, 1899 and 'D.' lobatus Laurie, 1899 were shown to be synonyms of the basal eurypterine Stoermeropterus conicus (Lamsdell 2011), Kokomopterus longicaudatus (Clarke & Ruedemann, 1912) was transferred from the genus by Kjellesvig-Waering (1966), D. ruedemanni O'Connell, 1916 was shown to be a lithic clast by Tollerton (2004), Vinetopterus struvei (Størmer, 1974) was removed by Poschmann & Tetlie (2004) and 'D.' nodosus Kjellesvig-Waering & Leutze, 1966 is considered congeneric with S. conicus. Therefore, aside from D. pentlandicus, only two other species of Drepanopterus are currently recognised as valid: D. abonensis Simpson, 1951 from the Upper Devonian of SW England and an unnamed species described by Braddy & Dunlop (2000) from the Lower Devonian of Arctic Canada. The genus received its most recent treatment when Drepanopterus abonensis was restudied by Lamsdell et al. (2009), where it was considered to have affinities with the large sweep-feeding mycteropoids, and subsequent phylogenetic analysis supports this theory (Lamsdell et al. 2010a). ...
... 4a). The initial size estimate of 70 cm given by Braddy & Dunlop is based on the old, incorrect reconstruction of Drepanopterus abonensis according to Simpson (1951). Scaling the Canadian specimens to the new reconstruction of Lamsdell et al. (2009) gives a size estimation of 40 cm. ...
Drepanopterus pentlandicus Laurie, 1892 is redescribed from the original type material along with previously unfigured specimens. A cleft metastoma is confirmed as a characteristic of the genus, along with the armature of the second and third prosomal appendages being modified into flattened blades, while the species is shown to possess a somewhat enlarged second tergite and lateral prosomal margins that overlap the first opisthosomal tergite. Different ontogenetic stages of D. pentlandicus are described, and reveal that these latter characters develop only later in ontogeny, suggesting that described specimens of Drepanopterus abonensis Simpson, 1951 may represent juveniles. Cladistic analysis of Stylonurina shows the genus Drepanopterus to be monophyletic consisting of D. pentlandicus, D. abonensis and D. odontospathus sp. nov.: it forms a basal clade of mycteropoids. Hibbertopteroidea Kjellesvig-Waering, 1959 is shown to be a junior subjective synonym of Mycteropoidea Cope, 1886, with the synonymy of many of the hibbertopterid genera hypothesised and Hibbertopterus Kjellesvig-Waering, 1959 suggested to represent juvenile specimens of Cyrtoctenus Størmer & Waterston, 1968. Hibbertopterus permianus Ponomarenko, 1985 is transferred to Campylocephalus Eichwald, 1860. The role of heterochrony in the morphological development of the mycteropoid lineage is discussed, with both hibbertopterids and mycteropids suggested to be hypertrophic and pre-displacement peramorphs respectively.
... It is a small structure (2 mm long, 5.5 mm wide) that preserves the anterior portion with a prominent embayment and is covered with anteriorly directed setae. The endostoma of the Devonian hibbertopterid eurypterid Drepanopterus abonensis Simpson, 1951 from the Old Red Sandstone was illustrated by Lamsdell et al. (2009). It is a rounded structure, 21 mm long, 28 mm wide, with a small posterior notch and long narrow anterior notch. ...
The endostoma of eurypterids is a small ventral structure previously known from only 11 specimens and in detail from only a single species, Eurypterus tetraganophthalmus. Four previously undescribed eurypterid specimens from the Samuel J. Ciurca Jr. Collection, Yale Peabody Museum of Natural History, likely belonging to Eurypterus, and a previously documented specimen of the pterygotid Acutiramus cummingsi in the New York State Museum, are considered here to reinterpret the morphology and homologies of the endostoma. We demonstrate that the endostoma is a bilateral, flaplike appendage, with distal margins bearing anteriorly facing setae. An anterior embayment and posterior medial notch are noted. The latter represents the point where the endostoma articulates with an oval sclerite. Here we propose that, contrary to previous interpretations, the endostoma is an appendage, likely of the seventh body segment, and is probably homologous to the xiphosuran chilaria. This has direct implications for the hypotheses of homology for the metastoma, a ventral structure common to eurypterids and chasmataspids.
The occurrences of Silurian scorpions, eurypterids, and xiphosurans in Scotland are summarised. Slimonia acuminata var. nov. hendersoni and Stylonurus knoxae sp. nov. are described. New morphological information is given concerning Hughmilleria conica (Laurie), Slimonia dubia (Laurie), Mixopterus dolichoschelus Størmer ex Laurie, Stylonurus ornatus Laurie, S. cf. macrophthalmus Laurie, and Drepanopterus pentlandicus Laurie.
Pentland Hills specimens from Green Cleuch and the Gutterford Burn date from the Upper Gala-Tarannon. Higher horizons in the Pentland Hills are not much later. The Lesmahagow faunas may perhaps not be more recent than Wenlock. The single Stonehaven species seems to be older than Downtonian.
Stylonurid eurypterids (Arthropoda: Chelicerata) include some of the largest known arthropods – bizarre sweep-feeding hibbertopterids from the Carboniferous to end-Permian. New material of Drepanopterus abonensis, a stylonurid from the Late Devonian (Famennian) of Portishead, south-west England, offers key insights into this genus and its affinities. A redescription utilising the new material enables D. abonensis to be assigned as basal member of the Superfamily Hibbertopteroidea, the large-sweep-feeding forms, possessing a cleft metastoma and blades (modified blunt spines) on their anterior prosomal appendages. D. abonensis also shares characters such as a clavate telson and median ridge on the carapace with the proposed hibbertopteroid sister group the Kokomopteroidea. Hibbertopteroid eurypterids are the most long-ranging stylonurids, surviving the decline and extinction of the other eurypterid families in the Late Devonian, their survival probably because of their sweep-feeding mode of life, which was not in direct competition with their eurypterine relatives and other predators.
Detailed examination of the Old Red Sandstone succession, which is unconformably overlain by Triassic Dolomitic Conglomerate, has permitted subdivision into twelve formations. The Lower Old Red Sandstone comprises cross-bedded sandstones but the younger rocks are more diversified and may be separated into conglomerate, sandstone and siltstone units. The Lower and Upper Old Red Sandstone contact is a conspicuous disconformity. The beds above and below the disconformable surface display layers of well-developed cornstone, which are interpreted as ancient caliche deposits. Cross-bedding studies show that the Old Red Sandstone sediments were mainly derived from the north-west.
A new eurypterid fauna from the Lower Bear Rock Formation (Early Devonian, Emsian) of Anderson River, in the Northwest Territories of the Canadian Arctic, is described. The material comprises an almost complete specimen and five isolated carapaces of Erieopterus microphthalmus; an incomplete carapace and telson referred to Drepanopterus sp.; and an isolated prosomal appendage of Carcinosoma sp. Associations include actinopterygian, sarcopterygian, and acanthodian fish, as well as lingulids, conchostracans, ostracodes, coprolites, and plant material. A nearshore marine environment is inferred. This assemblage provides the first Canadian record of Drepanopterus and the youngest Canadian occurrences of erieopterid and carcinosomatid eurypterids.
Whittard for assistance with the manuscript and to the Colston Society for a grant towards the cost of publication The Eurypterida of New York
- Literature Clarke
. The author is indebted to Professor W. F. Whittard for assistance with the manuscript and to the Colston Society for a grant towards the cost of publication. LITERATURE. CLARKE, J. M., and RUEDEMANN, R. 1912. " The Eurypterida of New York." Mem. 14 New York State Museum. Vols. I. and II.