A trigonotarbid arachnid from the Lower Devonian of Tredomen, Wales

An association of trigonotarbid arachnids from Siegenian strata of Burdenbach in the Westerwald is described. The Burdenbach trigonotarbids are numerically dominated by a new genus and species, Spinocharinus steinmeyeri n. gen. n. sp., which is characterized by a rounded carapace with a unique pattern of thorn-like tubercles. A comparison with previously described Devonian trigonotarbids suggests that the new taxon is most probably assignable to the family Palaeocharinidae, which is well represented by the genus Palaeocharinus from the Scottish Rhynie cherts. This would constitute the first record of Palaeocharinidae from the Rhenish Devonian and contrasts sharply with previously described Emsian associations from the Rhenish Slate Mountains, which are dominated by archaeomartids. A rare archaeomartid, Archaeomartus cf. levis, occurs in association with the putative palaeocharinids.

New material of the trigonotarbids Alkenia and Archaeomartus from the Lower Devonian type locality Alken an der Mosel/Germany is described. Stormer’s original description of Alkenia is essentially confirmed and supplemented. The genus is placed in Aphantomartidae. In contrast to earlier accounts, we show that Archaeomartus has an anterior diplotergite and a longitudinally three-divided posteriormost (ninth) tergite. The new family Archaeomartidae is proposed. Whether a marginal row of larger tubercles on the opisthosoma can be recognized is strongly influenced by the taphonomic history of the fossil, and sexual dimorphism may also be involved. Thus, we propose that Archaeomartus levis and A. tuberculatus, which can be discriminated solely by the presence or absence of this feature, are synonyms. Furthermore, morphological similarity suggests the possibility that archaeomartids, with their opisthosomal tergites divided into three plates, gave rise to the later (Carboniferous) anthracomartids, specifically through the division of the lateral plates and the ninth tergite. Finally, our reassessment of Archaeomartus shows that ‘A.’ roessleri Dunlop and Brauckmann, 2006 can no longer be adequately maintained in this genus. This younger species from the early Upper Carboniferous of Hagen-Vorhalle, Germany, is reassigned to Namurotarbus n. gen. as Namurotarbus roessleri n. comb.

In 1926 I recorded the occurrence of a Lower Devonian flora from the Senni Beds near Brecon, and described one new genus, Gosslingia , in detail. In 1931 a “thalloid-like” plant, Thallomia , from the Lower Downtonian of the Llandovery district, was recorded (Heard and Jones 1931). Other fragmentary plant remains are present in both the above localities, and it is the object of this communication to place on record some of the more interesting of these fossils. Most of the material is badly preserved, and has proved unsuitable for examination by transfer or “film-pull” methods. As previously recorded (Heard and Jones 1931, p. 552), the plant Thallomia occurs with a few fragments of dichotomously branched stems and obscure carbonaceous material at Capel Horeb near Llandovery. The fossil plants are associated with a lenticle of mudstone which is intercalated with the flaggy sandstones (Tilestones) of Lower Downtonian age. Only one fairly complete specimen was obtained by Mr. J. F. Jones, who found the plant bed (Pl. XII, fig. 1). This consists of a slender stem, about 4–5 cms. long and 0–8 mm. wide, which shows two dichotomous branchings. Each of the two upper and equal divisions of the stem is terminated by a capsule-like body (5 mm. by 2 mm.), which tapers at the base and has an obtuse end. This is regarded as a sporangium. A “film-pull” from these sporangia shows only a broken carbonaceous margin to the sporangium. No spores are to be seen. The greater part of the fossil

Traquairaspididae and Cyathaspididae (Heterostraci) from the Lower Devonian of Poland

Since 1876, when McCoy described two specimens of tuberculated plates under the name Asterolepis ornata var. australis, placoderm remains have been known to occur in the Middle Devonian marine limestones of Buchan, Victoria, Australia. Some years later, another specimen was obtained from the Buchan limestones by W. H. Ferguson of the Geological Survey of Victoria, and was referred by Chapman (1916) to the genus Phlyctaenaspis. Chapman, regarding McCoy's specimens as cospecific with the new material, included all the remains in the species Phlyctaenaspis australis (McCoy), distinguishing the more complete specimen discovered by Ferguson as P. australis var. confertituberculata Chapman. As Phlyctaenaspis is a form typical of the Lower Devonian, its reported occurrence in the Middle Devonian seemed to warrant further investigation. I therefore undertook a re-examination of all the available material, which is now preserved in the National Museum, Melbourne, and spent some months in removing the matrix from Ferguson's specimen. The matrix is a hard carbonaceous limestone containing remains of Spirifer yassensis and other invertebrates, and it was found that dilute hydrochloric acid would dissolve away this matrix without seriously affecting the fish plates, although care had to be taken not to subject these to too long contact with the acid. When as much of the matrix as possible had been removed mechanically by grinding, the fossil was exposed by brushing the dilute acid on to the remainder with a camel-hair brush, and continually observing the result under a binocular microscope.

A rare, complete specimen of Zlichovaspis (Zlichovaspis) rugosa rugosa (Hawle & Corda, 1847) with in situ articulated hypostome is described from the locality Tetín Hill near Beroun (Bohemia). This unique sample is stored in the Musée d'Histoire Naturelle de Lille (France). Dalmanitid trilobites with articulated hypostome represent very rare findings worldwide, although these trilobites show the conterminant type of the hypostome. Although these trilobites are a common component of Devonian communities inhabiting Prague Basin, only eight specimens with hypostome attached to the doublure and/or hypostome preserved very close to the doublure have been described; they all belong to the common species Zlichovaspis (Zlichovaspis) rugosa rugosa and Odontochile cristata Hawle & Corda, 1847, respectively. The newly described specimen represents most probably a carcass. It is the best preserved specimen of this species with hypostome in situ and provides the opportunity to reconstruct the 3D orientation of the hypostome and its relation to the cephalon for the first time. The possible causes of the apparent paucity of specimens with hypostome in situ in Devonian dalmanitid trilobites are discussed.

Some new impressions have been observed on the visceral surface of a dorsal shield of Ctenaspis sp. from the Lower Devonian of Spitsbergen. They indicate the probable position of the ophthalmicus profundus and o. lateralis nerves, and of two branchial nerves. The impressions left by the branchial arches are also visible on the same specimen. Furthermore, a median dorsal series of circular impressions previously observed in Seretaspis zychi StensiÖ is compared to similar impressions observed in two osteostracans, and it is suggested that vertebral elements were present in the Heterostraci. Finally, the affinities of the Heterostraci are discussed and it is suggested that they may represent the sister group of the Myopterygii (Cephalaspidomorphi + Gnathostomata).

Description d'une nouvelle espèce et analyse morpho-fonctionnelle du genre Doryaspis White (Heterostraci) du Dévonien du Spitsberg