Paleozoic Taxa Research Articles

The Evolution and Fossil History of Sensory Perception in Amniote Vertebrates

Sensory perception is of crucial importance for animals to interact with their biotic and abiotic environment. In amniotes, the clade including modern mammals (Synapsida), modern reptiles (Reptilia), and their fossil relatives, the evolution of sensory perception took place in a stepwise manner after amniotes appeared in the Carboniferous. Fossil evidence suggests that Paleozoic taxa had only a limited amount of sensory capacities relative to later forms, with the majority of more sophisticated types of sensing evolving during the Triassic and Jurassic. Alongside the evolution of improved sensory capacities, various types of social communication evolved across different groups. At present there is no definitive evidence for a relationship between sensory evolution and species diversification. It cannot be excluded, however, that selection for improved sensing was partially triggered by biotic interactions, e.g., in the context of niche competition, whereas ecospace expansion, especially during the Mesozoic, might also have played an important role.

Paleobotanical study of a section of the Oligocene–Lower Miocene Maikop Group along the Belaya River above the city of Maikop, Ciscaucasia

A stratotypical section of the Oligocene–Lower Miocene Maikop Group in the valley of the Belaya River above the city of Maikop was studied using a complex paleobotanical method. The hydrological regime of marine basin was specified, especially for the second half of the Early Oligocene, when the basin was brackish. Its desalination began prior to accumulation of the ostracod layers and continued until the beginning of the Late Oligocene. It was once interrupted by short-term ingression of seawater into the Paratethys in the Early Morozkina Balka time. The Karadzhalga and Septarian formations were formed at the end of the Oligocene and in the Early Miocene under frequent oscillations of climate and hydrological regime with accumulation of sediments within the Laba delta front. The complexes of plant microfossils, along with dominant recent marine organic-walled freshwater phytoplankton, contain algae, spores, pollen, and a huge amount of redeposited palynomorphs. They originated from areas of erosion and included Paleogene, Mesozoic, and, locally, Paleozoic taxa.

Temporal trends of predation resistance in Paleozoic crinoid arm branching morphologies

The rise of durophagous predators during the Paleozoic represents an ecological constraint imposed on sessile marine fauna. In crinoids, it has been suggested that increasing predation pressure drove the spread of adaptations against predation. Damage to a crinoid's arms from nonlethal predation varies as a function of arm branching pattern. Here, using a metric for resilience to predation (“expected arm loss,” EAL), we test the hypothesis that the increase in predation led to more predation-resistant arm branching patterns (lower EAL) among Paleozoic crinoids. EAL was computed for 230 genera of Paleozoic crinoids and analyzed with respect to taxonomy and time. The results show significant variability among taxa. Camerates, especially monobathrids, display a pattern of increasingly convergent and predation-resistant arm morphologies from the Ordovician through the Devonian, with no significant change during the Mississippian. In contrast, the mean EAL among cladids follows no overall trend through the Paleozoic. Regenerating arms are known to be significantly more common in camerates than in other Paleozoic taxa; if regeneration is taken as a proxy for nonlethal interactions with durophagous predators, this indicates that nonlethal predation occurred more often among camerates throughout the Early and Middle Paleozoic. In addition, frequency of injury among camerates is inversely correlated with EAL and positively correlated with infestation by parasitic snails. From this we conclude that decreasing EAL signals a selective pressure in favor of resistance to grazing predation in camerates but not in other subclasses before the Mississippian, with an apparent relaxation in this constraint after the late Devonian extinctions.

Dental patterning in the earliest sharks: Implications for tooth evolution

Doliodus problematicus is the oldest known fossil shark-like fish with an almost intact dentition (Emsian, Lower Devonian, c. 397Ma). We provide a detailed description of the teeth and dentition in D. problematicus, based on tomographic analysis of NBMG 10127 (New Brunswick Museum, Canada). Comparisons with modern shark dentitions suggest that Doliodus was a ram-feeding predator with a dentition adapted to seizing and disabling prey. Doliodus provides several clues about the early evolution of the "shark-like" dentition in chondrichthyans and also raises new questions about the evolution of oral teeth in jawed vertebrates. As in modern sharks, teeth in Doliodus were replaced in a linguo-labial sequence within tooth families at fixed positions along the jaws (12-14 tooth families per jaw quadrant in NBMG 10127). Doliodus teeth were replaced much more slowly than in modern sharks. Nevertheless, its tooth formation was apparently as highly organized as in modern elasmobranchs, in which future tooth positions are indicated by synchronized expression of shh at fixed loci within the dental epithelium. Comparable dental arrays are absent in osteichthyans, placoderms, and many "acanthodians"; a "shark-like" dentition, therefore, may be a synapomorphy of chondrichthyans and gnathostomes such as Ptomacanthus. The upper anterior teeth in Doliodus were not attached to the palatoquadrates, but were instead supported by the ethmoid region of the prechordal basicranium, as in some other Paleozoic taxa (e.g., Triodus, Ptomacanthus). This suggests that the chondrichthyan dental lamina was originally associated with prechordal basicranial cartilage as well as jaw cartilage, and that the modern elasmobranch condition (in which the oral dentition is confined to the jaws) is phylogenetically advanced. Thus, oral tooth development in modern elasmobranchs does not provide a complete developmental model for chondrichthyans or gnathostomes.

Morphometric analysis of skeletal growth in the lepospondyls Microbrachis pelikani and Hyloplesion longicostatum (Tetrapoda, Lepospondyli)

ABSTRACT Although morphological evidence alone appears insufficient to resolve the problem of extant amphibian ancestry, comparison of developmental processes and functional correlates of ontogenetic change may provide a basis for evaluating relationships among extinct and extant tetrapods. In the first allometric study of cranial and postcranial growth in any lepospondyl, I investigate skeletal development in the microsaurs Microbrachis pelikani and Hyloplesion longicostatum using traditional measurement-based and geometric morphometric analyses. Regression analyses against both skull and centrum lengths for M. pelikani indicate positive allometric scaling of the interclavicle plate length, pubis, and ilium, and negative scaling of the diameter of the orbit. Preliminary data for H. longicostatum support negative scaling of neural arch height and posterior centrum height. Results from geometric morphometrics suggest slight widening of the cheek in M. pelikani, rather than marked elongation. Overall, cranial and postcranial growth in both microsaurs was primarily isometric and comparison with allometric data from other Paleozoic taxa suggests that isometric growth is an ancestral feature of development in early tetrapods. All regression analyses for M. pelikani and H. longicostatum had a constant linear slope, indicating that ontogenetic trajectories were continuous, with gradual skeletal growth and no shift in feeding or locomotor function during ontogeny. The lack of morphological change suggests that these microsaurs did not undergo an extant amphibian-like metamorphosis that included reorganization of the skeleton. These data support the hypothesis that metamorphosis is a derived mode of development present only in extant amphibians and their closest relatives. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

The lissamphibian humerus and elbow joint, and the origins of modern amphibians

The origins and evolution of the three major clades of modern amphibians are still a source of controversy, and no general consensus exists as to their relationship to the various known Paleozoic taxa. This may indicate that additional character complexes should be studied to resolve their phylogenetic relationship. The salamander elbow joint has been fundamentally misinterpreted in previous morphological descriptions. In caudates and anurans, both the radius and ulna (fused in anurans) articulate with the characteristically large capitulum (radial condyle), although part of the ulnar articulating surface fits into to the smooth trochlear region. The salamander "ulnar condyle" of previous descriptions is in fact the entepicondyle. The condition seen in batrachians (i.e., salamanders and frogs) may be a lissamphibian synapomorphy because the elbow region of the primitive fossil caecilian Eocaecilia resembles those of frogs and salamanders. In addition to the large and bulbous capitulum, all lissamphibian humeri lack an entepicondylar foramen, and possess a distally pointing entepicondyle, a low and rounded ectepicondyle, and an elongated shaft. These characters are identified in key fossil forms to assess the support for the different hypotheses proposed for the evolutionary origins of lissamphibians. Temnospondyli is the only group of early tetrapods that shows a progressive evolution of lissamphibian traits in the humerus and elbow joint. Furthermore, among Paleozoic taxa, the dissorophoid temnospondyl Doleserpeton annectens is the only taxon that has the full set of humeral features shared by all lissamphibians. These results add support for the theory of a monophyletic origin of lissamphibians from dissorophoidtemnospondyls.

Catalogue of Recent and fossil taxa of the family Architectonicidae Gray, 1850 (Mollusca: Gastropoda)

The marine gastropod family Architectonicidae (= Solariidae), commonly known as sundials, comprises about 140 worldwide extant species classified in 11 genera. More than ten times as many names are used in the literature for both Recent and fossil taxa, the latter dating from the Mesozoic (Paleozoic taxa were misinterpreted). Herein we catalog more than 1550 names that have appeared in print at the family-group (10), genus-group (137), and species-group levels (1408). Of the last, nearly 1100 are found to be nomenclatorially available or potentially available. An Appendix is included in which nomenclatural changes are made and/or commented upon. It is demonstrated that Solarium maculatum Link, 1807 was validly introduced and, as Architectonica maculata (Link, 1807), becomes the valid name for the species usually cited as A. picta (Philippi, 1849). The invalid introduction of Heliacus messanensis Bertolaso & Palazzi, 2000 is discussed. The emended spelling of the specific name in the binomen Solatisonax alleryi (G. Seguenza, 1876) is shown to be correctly accepted. Philippia lepida Bayer, 1942, Torinia gyrus depressiusculaBayer, 1848, Solarium subconcolor von Martens, 1880, Solarium conulus Weinkauff, 1868 and Solarium submoniliferum d’Orbigny, 1852 were proposed as replacement names for multiple preoccupied names and/or misidentifications. These are here restricted to avoid possible confusion. The history and current status of the similarly spelled and inconsistently used nomina Fluxiella and Fluxinella (as placed in Architectonicidae and/or Seguenziidae) are discussed.

PAEDOPRONORITES, A NEW UPPER PERMIAN (WUCHIAPINGIAN) AMMONOID FROM INDONESIA (TIMOR)

Representatives of the ammonoid family Pronoritidae are ancestral medlicottioideans (Order Prolecanitida) characterized by moderately evolute conch and relatively simple sutures. They comprise the ancestral Pronoritinae, characterized by an undivided dorsal lobe, and the descendant Neopronoritinae with bidentate dorsal lobe. The new genus Paedopronorites is interpreted as the terminal neopronoritin paedomorph. It conforms to the pattern displayed by many late Paleozoic taxa (Glenister and Furnish, 1988a, 1988b), being the geologically youngest representative in the lineage, and characterized by small size, sutural simplification, and low abundance. Pronoritidae form one of the longer lineages of Paleozoic ammonoids, with few changes occurring from Mississippian (lower Visean) to …

The importance of global parsimony and historical bias in understanding tetrapod evolution. Part I. Systematics, middle ear evolution and jaw suspension

A phylogenetic analysis based on a data matrix of 43 taxa and 155 osteological characters has produced a new hypothesis of tetrapod phylogeny that is drastically different from the established consensus. Among Paleozoic taxa, only diadectomorphs appear to be related to amniotes. In contrast to previous hypotheses, lissamphibians appear to have been derived from lepospondyls. Seymouriamorphs, gephyrostegids, embolomeres, temnospondyls, and loxommatids are stem-tetrapods. The new phylogeny suggests that the absence of a tympanic middle ear in salamanders and gymnophiones is a primitive character.

Crescenticythere, a new enigmatic ostracode from the Tertiary of New Zealand

During examination of the large ostracode assemblage collections at the Department of Scientific and Industrial Research, Geology & Geophysics, Lower Hutt, New Zealand, a single specimen of unusual shape was encountered. So unusual is the crescentic outline and infolding of the entire shell periphery that assignment even to a phylum was difficult, and it was only upon scanning electron microscopic study that subcentral muscle scars were clearly observed and these enabled confident identification of the specimen as an ostracode. One specimen is not usually considered sufficient to propose a new taxon; however, in this case there is no doubt that this unique specimen clearly represents a new species, genus, and probably family of Ostracoda. A search for additional specimens from the type unit is underway, but has, as yet, been unsuccessful to find this rare intriguing ostracode. Unlike other unusual ostracodes described from the Southern Hemisphere such as the punciids, this specimen appears to have no similarity with Paleozoic taxa.

Fossil Mycorrhizae: A Case for Symbiosis

Vesicular-arbuscular mycorrhizae are significant in the physiology and ecology of extant vascular plants, and they may also have played a major role in the origin of the vascular land flora. The case for fossil vesicular-arbuscular mycorrhizae rests upon hyphae and chlamydospore-like bodies in several Paleozoic taxa, but fossil arbuscles are unknown to date. Specimens from the Triassic of Antarctica represent the first known occurrence of arbuscles in the fossil record.