Carboniferous Forms Research Articles

A new fossil mantis shrimp and the convergent evolution of a lobster-like morphotype.

Eumalacostracan crustaceans all have a more or less stereotypic body organisation in the sense of tagmosis. Originally, this included a head with six segments (ocular segment plus five appendage-bearing segments), a thorax region with eight segments, and a pleon with six segments. Interestingly, despite these restrictions in variability in terms of tagmosis, the morphological diversity within Eumalacostraca is rather high. A group providing representative examples that are commonly known is Decapoda. Decapodan crustaceans include shrimp-like forms, lobster-like forms and crab-like forms. The stem species of Eucarida, the group including Decapoda and Euphausiacea, presumably possessed a rather shrimp-like morphology, quite similar to the stem species of Eumalacostraca. Also two other lineages within Eumalacostraca, namely Hoplocarida (with the mantis shrimps as modern representatives) and Neocarida (with the sister groups Thermosbaenacea and Peracarida) evolved from the shrimp-like body organisation to include a lobster-like one. In this study, we demonstrate that the stepwise evolution towards a lobster morphotype occurred to a certain extent in similar order in these three lineages, Hoplocarida, Eucarida and Peracarida, leading to similar types of derived body organisation. This evolutionary reconstruction is based not only on observations of modern fauna, but especially on exceptionally preserved Mesozoic fossils, including the description of a new species of mantis shrimps bridging the morphological gap between the more ancestral-appearing Carboniferous forms and the more modern-appearing Jurassic forms. With this, Mesozoic eumalacostracans represent an important (if not unique) ‘experimental set-up’ for research on factors leading to convergent evolution, the understanding of which is still one of the puzzling challenges of modern evolutionary theory.

Phylogenetic and environmental context of a Tournaisian tetrapod fauna.

The end-Devonian to mid-Mississippian time interval has long been known for its depauperate palaeontological record, especially for tetrapods. This interval encapsulates the time of increasing terrestriality among tetrapods, but only two Tournaisian localities previously produced tetrapod fossils. Here we describe five new Tournaisian tetrapods (Perittodus apsconditus, Koilops herma, Ossirarus kierani, Diploradus austiumensis and Aytonerpeton microps) from two localities in their environmental context. A phylogenetic analysis retrieved three taxa as stem tetrapods, interspersed among Devonian and Carboniferous forms, and two as stem amphibians, suggesting a deep split among crown tetrapods. We also illustrate new tetrapod specimens from these and additional localities in the Scottish Borders region. The new taxa and specimens suggest that tetrapod diversification was well established by the Tournaisian. Sedimentary evidence indicates that the tetrapod fossils are usually associated with sandy siltstones overlying wetland palaeosols. Tetrapods were probably living on vegetated surfaces that were subsequently flooded. We show that atmospheric oxygen levels were stable across the Devonian/Carboniferous boundary, and did not inhibit the evolution of terrestriality. This wealth of tetrapods from Tournaisian localities highlights the potential for discoveries elsewhere.

Redescription of the lungfish Straitonia waterstoni from the Viséan of Lothian, Scotland

ABSTRACTThe unique specimen of the Early Carboniferous lungfish Straitonia waterstoni is described in detail. As the only articulated lungfish currently described from the Viséan, it is of particular interest for lungfish evolution. It retains some plesiomorphic features of the skull, and shows some derived features in common with later Carboniferous forms. A thorough description is provided for future phylogenetic analyses. Straitonia has a number of diagnostic features. These include: a relatively narrow B-bone with a broad and curved anterior margin; an unpaired, parallel-sided C-bone whose margin is convex anteriorly; a B-bone approximately the same width as the single C-bone; the I-bones are relatively small compared with the B- and J-bones; the J-bones are tri-lobed; the XY bone is elongate along a posteromedial–anterolateral axis. Elongate fins dorsally and ventrally suggest a condition similar to those of later Carboniferous forms with confluent second dorsal, caudal and anal fins. It may thus be the earliest lungfish to show this condition. The ventral tail fin includes some fused elements, probably haemal and infrahaemal spines. The identity of one of the skull bones is discussed, and concluded to be a C-bone rather than a D-bone as previously described. The D-bone is absent, as in later Carboniferous forms. The history of the D-bone is considered.

Morphology and wall ultrastructure of the megaspore Lagenicula (Triletes) variabilis (Winslow, 1962) Arioli et al. (2004) from the Lower Carboniferous of Ohio, USA

Megaspores assigned to Lagenicula (Triletes) variabilis (Winslow, M., 1962. Plant spores and other microfossils from Upper Devonian and Lower Mississippian Rocks of Ohio. Geol. Surv. Prof. Pap. 364, 1–93) Arioli et al., 2004, from the Lower Carboniferous (Tournaisian) of northeastern Ohio, USA, have been analysed using light microscopy (LM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). These studies provide new information on morphology, gross structure and wall ultrastructure. Previous reports of in situ megaspores indicate that Upper Carboniferous Lagenicula (and related forms) derive from the Lepidocarpaceae, that include many of the large arborescent lycopsids that dominated the Euramerican Coal Measure forests. Based on morphological and, to a lesser extent, ultrastructural similarities with Upper Carboniferous forms, it seems likely that Lower Carboniferous Lagenicula also derive from similar plants. This suggests that large arborescent lycopsids typical of the Upper Carboniferous (or at least their precursors) were already present in the Lower Carboniferous, possibly forming forests in similar environments. These may be underrepresented in the fossil record because of the paucity of deposits of this age representing such environments.

An early tetrapod from 'Romer's Gap'.

The fossil record of early tetrapods has been increased recently by new finds from the Devonian period and mid-late Early Carboniferous period. Despite this, understanding of tetrapod evolution has been hampered by a 20-million-year gap ('Romer's Gap') that covers the crucial, early period when many key features of terrestrial tetrapods were acquired. Here I describe the only articulated skeleton of a tetrapod, Pederpes, yet found from the Tournaisian epoch (354-344 million years ago (Myr)). The new taxon includes a pes with five robust digits, but a very small, possibly supernumerary digit preserved on the manus suggests the presence of polydactyly. Polydactylous early tetrapods may have survived beyond the end of the Devonian and pentadactyly cannot be assumed for the pes. However, the pes has characteristics that distinguish it from the paddle-like feet of the Devonian forms and resembles the feet of later, more terrestrially adapted Carboniferous forms. Pederpes is the earliest-known tetrapod to show the beginnings of terrestrial locomotion and was at least functionally pentadactyl. With its later American sister-genus, Whatcheeria, it represents the next most primitive tetrapod clade after those of the Late Devonian, bridging the temporal, morphological and phylogenetic gaps that have hitherto separated Late Devonian and mid-Carboniferous tetrapod faunas.

Diversity of exine structure in Upper Carboniferous (Westphalian) selaginellalean megaspores

Studies of wall structure in Mesozoic and Recent selaginellalean megaspores have been well documented. However, Palaeozoic examples have received minimal attention. The principal Palaeozoic megaspore genus of likely selaginellalean affinity is Triangulatisporites, extending from the Upper Devonian to the Upper Carboniferous. The particulate wall ultrastructure of a previously published Carboniferous (Duckmantian) megaspore assigned to this genus suggested that this form of wall construction may have been the ancestral wall structure of the group, an observation which posed difficulties in relating selaginellalean ultrastructure to that of other contemporaneous lycopsid megaspores. Subsequent investigation showed that the genus also contains more laminate exines similar to those of other extinct lycopsids and extant Selaginella species. Our new examples of Triangulatisporites ultrastructure from the Langsettian, Duckmantian and Westphalian D yield more information regarding early variation of wall structure within Carboniferous selaginellalean megaspores and suggest that a more laminate wall composition is at least as old as the particulate form. However, without further investigation of Lower Carboniferous forms, we are unable to state which is indeed ancestral. The laminate structure reported here and elsewhere is, none the less, more easily related to comparable ultrastructure in other groups of Carboniferous lycopsid megaspores and could suggest a link with such genera as Zonalesporites and early Lagenicula. This would be in keeping with current concepts regarding the most primitive ultrastructural type within lycopsid megaspore walls.

Origins of some Early Carboniferous calcrete fabrics revealed by cathodoluminescence: implications for interpreting the sites of calcrete formation

Calcretes from the Lower Carboniferous marginal marine limestones of South Wales, Germany and Belgium exhibit complex calcite microspar fabrics with rhombic, irregular and spherical crystals in variable mosaics. While many of these fabrics resemble classic recrystallization microspars, having irregular crystal forms and non-planar crystal boundaries, cathodoluminescence microscopy reveals that they result from multiple phases of precipitation and dissolution. No evidence for recrystallization by crystal boundary migration or replacement during the transformation of less stable calcite minerals (aragonite or high-magnesian calcite) is seen. Identical microspar fabrics have been widely described in Quaternary calcareous soils, which may also be primary fabrics and not due to recrystallization or mineral transformation. Cathodoluminescence provides a useful tool for interpreting calcrete fabrics and, in the case of these Carboniferous forms, indicates multiple phases of carbonate saturation and leaching reflecting the prominent wetting and drying phases evidenced by associated vertic soils horizons. The complex cycles of precipitation and dissolution are characteristic of pedogenic calcretes, and the recognition of such features using cathodoluminescence may provide a means of differentiating pedogenic from groundwater calcretes.

Palaeozoic, Mesozoic and contemporaneous megaspores from the Tertiary of southern England: indicators of sedimentary provenance and ancient vegetation

Megaspores are recorded from several localities in the Thanet and Reading Beds (upper Palaeocene) of southern England. Evidence from their taxonomic affinity, colour, compression and state of preservation indicates three separate groups: two reworked from lower Westphalian Coal Measures and Lower Cretaceous sequences, respectively, and one of contemporaneous forms. Mesozoic megaspores redeposited in the British Tertiary have not previously been recorded. Isolated Carboniferous forms have been found before but their possible value in provenance studies has not been fully explored. The new material includes a diverse assemblage of numerous Westphalian and Lower Cretaceous forms from a single horizon in the Thanet Beds. Of possible source areas it seems most likely that these spores were reworked from the Moray Firth Basin, and elsewhere near the present eastern coast of Scotland, by means of longshore drift following a roughly N–S palaeocoastline. Evidence from other studies of heavy mineral assemblages and palaeogeography also indicates derivation of Thanet Beds sediments by this means. The Cenozoic megaspores include an Azolla (water fern) and two distinct lycopsid forms, one probably of selaginellalean and one of isoetalean affinity. These latter provide the first clear evidence of lycopsids in British Tertiary floras and expand our knowledge of freshwater macrophytes of that time. The assemblages of Minerisporites show morphological trends which may prove to be of biostratigraphic value.

A new genus and species of anthracosaur amphibian from the Lower Carboniferous of Scotland and the status ofPholidogaster pisciformisHuxley

The isolated skull of a Lower Carboniferous anthracosaur labyrinthodont from the Midlothian coalfield was formerly but erroneously attributed toPholidogaster pisciformis. It is now redescribed after ‘Airbrasive’ development as the holotype of a new genus and species. The anthracosaur agrees in a number of diagnostic cranial characters with the embolomerous forms of the Coal Measures but other characters, particularly those of the braincase and lower jaw, suggest relationship to the Seymouriamorpha. Its cranial anatomy could well be antecedent to that of both these groups and the sparse evidence available suggests close relationship to the American Mississippian anthracosaurProterogyrinus. A new classification of the Batrachosauria is presented with a major subdivision into Anthracosauria and Seymouriamorpha. The former group comprises the newly proposed infraorder Herpetospondyli to include the Lower Carboniferous forms, together with the infraorders Embolomeri and Gephyrostegoidea. It is concluded that while no batrachosaur with an otic notch could be a reptile ancestor a primitive ‘notchless’ anthracosaur could be. The cranial anatomy ofPholidogaster pisciformisis then redescribed, after complete ‘Airbrasive’ preparation of the holotype skull. The holotype, like the anthracosaur, comes from the Gilmerton Ironstone of the Edinburgh region, but the earlier holotype skull ofOtocratia modesta, long considered to be an ichthyostegid, is also attributed toPholidogaster. After redescription of ‘Otocratia' a composite restoration of thePholidogasterskull is presented. The nature of the dermal ornament, the post-parietal-supratemporal suture, the absence of tabular horns and the nature of the post-cranial skeleton all demonstrate thatPholidogasteris an early temnospondyl labyrinthodont in no way closely related to anthracosaurs. It is closely similar to the American Mississippian formGreererpeton burkemoraniRomer, notably in the presence of large premaxillary fangs and the absence of otic notch and intertemporal. Both may be attributed to the family Colosteidae. It is concluded that there is no strong evidence of close relationship between the colosteids and the Devonian ichthyostegids.

LINOPROTONIA, A NEW GENUS OF LOWER CARBONIFEROUS PRODUCTOID

Summary Productus hemisphaericus J. Sowerby is redescribed and designated type species of the new genus Linoprotonia. Productus corrugatohemisphericus (Vaughan) is also redescribed and referred to the genus, together with Linoprotonia ashfellensis sp. nov. which is common in north-west England and has often been erroneously referred to P. corrugatohemisphericus. Other previously described Lower Carboniferous species showing similar external form to Linoproductus are considered to belong in the new genus Linoprotonia. An attempt is made to show the relationship between these Lower Carboniferous forms and the gigantoproductids, linoproductids and striatiferids. It is suggested that these genera may form a phylogenetic lineage.

The cone of Cyclostigma kiltorkense Haughton, from the Upper Devonian of Ireland

Cyclostigma kiltorkense Haughton (Upper Devonian, Ireland) is preserved as a compression fossil in which the plant material has been replaced by chlorite. Surprisingly fine detail is observable when the material is immersed in xylene. Re -examination of old material, and specimens from a new exposure at Kiltorcan Hill shows that the leaf scar has parichnos cicatricules but no evidence of a ligule. The cone is heterosporous, with a, Lepidostrobus organization to the cone, and the sporophyll lamina has a fimbriate margin. The megaspores have an apical prominence and spines, and conform to the dispersed spore genus Lagenicula. One mega-spore appears to have germinated, to form a protruding gametophyte. Cyclostigma is closer to Carboniferous forms than to any Devonian lycopod.

The faunas of the Tournaisian Tulcumba Sandstone and its members in the Werrie and Belvue synclines, New South Wales

Abstract The faunas of the Tulcumba Sandstone and its member, the Rangari Limestone, from the western edge of the Werrie and Belvue synclines of western New England are described. The stratigraphical and palaeontological data are considered to indicate a Tournaisian (Kinderhookian) age. The gastropods and lamellibranchs include several Devonian holdovers, and the affinities of the brachiopods are as much with late Devonian as with Carboniferous forms. The trilobite genus Australosutura is shown to be much longer ranging than was previously thought to be the case. Most of the species described are new and are not known from units higher in the Carboniferous in New South Wales. One new chonetoid brachiopod genus, Tulcumbella with type species T. microstriata n.sp., and one new trilobite genus Weania, with type species W. goldringi n.sp., are described. Other new brachiopods are Acanthatia rangariensis, Spirifer lirellus sol, Tylothyris minima, Brachythyris solida and Cranaena concava. New polyzoans are Evac...

Discussion

The P resident asked whether the author had considered the possibility that, in some cases illustrated, the epifauna had settled on the shell after the death of the brachiopod; he referred in particular to the lantern-slide showing epifauna on the brachiopod interarea. Professor T. N eville G eorge referred to the occurrence of similar epifaunal associations on shells of both Silurian and Carboniferous age in rocks of comparable facies. Eospirifer from the Wenlock Limestone not uncommonly was a base for attachment of both polyzoans and auloporoid corals, and “ Spirifer ” in Tournaisian and Viséan shales of a variety of sessile forms including Cladochonus and serpulids. There was, however, no obviously preferred shell-type as host; and other brachiopods, including pentameraceans and orthaceans in Wenlock rocks, and productaceans and orthotetaceans in Carboniferous, were as often the convenient base as spirifers —and molluscs in the Lias as often as Spiriferina. There was little doubt that the “selection” of a base by an attached form was completely accidental: in life-history the change from a planktonic to a benthic habit by the growing individual was a passive fall onto a randomly variable sea-floor, with survival dependent on the chance of attachment to whatever hard base scattered shells might provide. The concentration of epifaunal growth on the stouter dorsal valve of the spirifers was also a feature of Silurian and Carboniferous forms, and, combined with the usually clear umbones and interarea, suggested the life-posture of the spirifers to be as the author inferred. The delthyrial structures of those few spirifers

XVI.— Naiadites from the Lower Carboniferous of Scotland : a Variation Study

The following is the first of a series of detailed variation studies of the non-marine lamellibranchs of the Lower Carboniferous of Scotland. Most of the forms have already been described by R. Etheridge, Jun. (1878), Hind (1894-5), and others. In the light, however, of more comprehensive methods in the revision of the Coal Measures species it has become essential to revise the Lower Carboniferous forms, and by statistics and illustration to define the course of variation within each species. The Lower Carboniferous rocks of Scotland differ from those of much of Southern Britain in the occurrence of thick series of estuarine deposits (the Calciferous Sandstone Series and the Limestone Coal Group): the non-marine faunas which they yield are thus of particular importance in relation to these investigations. Naiadites obesa and N. tumida (both R. Etheridge, Jun.) are by far the most abundant forms in the Lower Carboniferous. N. obesa occurs in great numbers on several horizons in the Calciferous Sandstone Series, while N. tumida is confined to the Limestone Coal Group. They are considered together, because, although Etheridge described them as separate species, Hind considered that he was dealing with one species, N. obesa. The writer agrees that they are closely related and in fact belong to one species-group, but considers that Hind's statement that Etheridge's descriptions offer no real point of distinction cannot be accepted, for the two types are easily distinguished and the distinguishing characters are stated in Etheridge's descriptions. In the following descriptions the conventional directions of This 250-word extract was created in the absence of an abstract The writer wishes to thank Professor D. I. Innes and Dr. G. A. Cumming of St. Andrews University for assistance in the field, and Professor A. E. Trueman, F.R.S. and Dr. J. Weir for advice and criticism. Thanks are also due to the Geological Survey for the loan of specimens. It should be recorded that the work was begun during the tenure of a Carnegie Teaching Fellowship in the University of Glasgow.

On the Permian Coelacanth, Coelacanthus granulatus, Ag

1.IntroductionAlthough the Permian species of Coelacanth, Coelacanthus granulatus, has been known since 1829, and although many authors have described specimens of it, it has remained unfortunately one of the lesser known of all Coelacanths. Since C. granulatus is the genotype of Coelacanthus, and since all the Carboniferous and some Triassic species have been assigned to this genus, it is surprising that further description has not been forthcoming. One of us (J. A. M. T.) has for some time been working on the Carboniferous Coelacanths, and it has been impossible to determine whether these really belong to the genus Coelacanthus. Accordingly it was hoped that by re-examining all the available material a more diagnostic description might be given. In doing this the authors have only been partly successful, as some of the most important generic characters—the dermal bones of the cheek and snout—were not preserved in any of the material examined. However, sufficient diagnostic characters have been provided by this research to distinguish the Carboniferous forms from this Permian genus.

Ambocœlia Hall and certain Similar British Spiriferidæ

Several small Spirifers of the Upper Palæozoic rocks of this country have been referred to Ambocœlia Hall. This genus was proposed to include certain American Devonian and Carboniferous forms with a peculiar internal structure; the genotype, designated by Hall, is Orthis umbonata Conrad, a species from the Hamilton Group (Lower Devonian) of North America. In the paper in which he established the genus, Hall (1860, p. 71) suggested that Spirifer unguiculus Sowerby sp. (a British Devonian form) might also be included in the genus. The opinion generally held, for example by King (1850, p. 135) and Davidson (1858, vol. ii, pt. 4, p. 59), that Spirifer unguiculus is closely allied to, if not identical with, Spirifer urei Fleming and Martinia clannyana King, led observers to place these species also in the genus Ambocœlia . It naturally followed that, so far as the British species were concerned, the genus was described in terms of the external form of these species. In particular, emphasis was laid upon the presence of a dorsal valve considerably flatter than the ventral, and upon the development of a more or less narrowly defined median sulcus in the former. Such a procedure resulted in a neglect of the internal features that Hall so clearly distinguished. Further, the discovery of spines in Martinia clannyana , and later in Spirifer urei , led to a belief that a spinose surface is also characteristic of the genus. In no instance, so far as I am aware, has any reference been made to the

A Synopsis of the American Arachnids of the Primitive Order Ricinulei

Ricinulids are peculiar looking arachnids which resemble superficially spiders, but are readily distinguished from the latter since they have a segmented abdomen and are without eyes. They constitute the rarest order of all the arthropods in number of specimens taken and in number of locality records obtained. Although the group is represented by well preserved carboniferous fossil forms in the North Temperate Zone, the only living examples of this order have been taken from the tropics, and in the past from two restricted areas. One of these is along the central west coast of Africa and the other is in the upper Amazon region.

IV. Contributions to the knowledge of lower carboniferous plants. I.—On the genus Rhacopteris, Schimper . II.—On the morphology of Sphenopteris Teiliana, Kidston, and its bearing on the position of the fructification on the frond of some lower carbon­iferous plants

The genus Rhacopteris was instituted by Schimper in 1869 for a type of fern-like frond of Carboniferous Age. It included one species Rhacopteris elegans , Ettingshausen sp. In 1879 the conception of the genus was extended and the following species were included: Rhacopteris inæguilatera and R. petiolata , Göppert spp., R. paniculifera and R. transitionis , Stur spp., R. speciosa , Ett., and Rhacopteris sp . Gomes. The Upper Carboniferous representatives differ in some respects from those of the Lower Carboniferous, and Oberste-Brink suggests a subdivision of the genus into Eurhacopteris and Anisopteris ; Eurhacopteris , including the Upper Carboniferous forms, R. elegans , Ett. sp., R. asplenites , Gutbier sp., R. dubia , Lindley and Hutton sp., R. Busseana , Stur, and R. Moyseyi , Arber; Anisopteris , including all the Lower Carboniferous forms. Oberste-Brink regards this as a more natural grouping of the constituents of Rhacopteris , Schimper, considering, moreover, that it receives support from the fact that this division of the genus corresponds to a stratigraphical separation of no small order. Oberste-Brink states that no Rhacopterids have been recorded from strata lying between the Middle Productive (Westphalian Series, Upper Carboniferous) Measures and the Culm (Lower Carboniferous). Since it is doubtful whether the division of the genus he suggests is a natural one, and not one with a stratigraphical bias, it seems on the whole inadvisable to adopt this nomenclature. The term Rhacopteris is of such widespread use among authors for these Lower Carboniferous fronds that it would merely increase the synonymy without any obvious advantage from the point of view of the systematist. We are concerned only with the Lower Carboniferous species in this communication. The fern-like fronds of Rhacopteris are characteristically pinnate, linear, and contracted towards the base. The pinnules are opposite or alternate, often asymmetric, contracted at the base, entire or divided into lobes, each of which has one or more veins. The texture of the lamina in many of the species was probably coriaceous. No midrib is present in the pinnule, but in some species by a series of unilateral dichotomies a one-sided arrangement results, from which it appears that a main vein passing along the lower margin of the pinnule gives rise to a series of more or less equal veins, which traverse the lamina to the upper margin, dichotomising one or more times on the way. No anastomoses have been observed between the veins.

VII.—Note on Eurypterus from the Carboniferous

In the Geological Magazine for November last (Decade III. Vol. IV. p. 481, Pl. XIII.) I gave a brief description of a new species of Eurypterus from the Lower Carboniferous Shales, Eskdale, Scotland, which I named Eurypterus scabrosus.I referred to other Carboniferous forms, and briefly mentioned one from the Lower productive Coal-measures, Darlington, Pennsylvania, U.S.A., figured as a woodcut only in the American Phil. Soc. Proc. vol. xix. p. 152, 1881.

II.—On some Specimens of Dithyrocaris from the Carboniferous Limestone series, East Kilbride, and from the Old Red Sandstone of Lanarkshire

The nine specimens of Phyllopodous Crustacea about to be noticed are, with one exception (that from Lanarkshire), all from the undoubted Carboniferous Limestone series, East Kilbride, a locality already well known to local geologists as having yielded a very rich series of Carboniferous forms.