The periotic of Moeritherium (Mammalia, Proboscidea): homology or homoplasy in the ear region of Tethytheria McKenna, 1975?

The periotic of Moeritherium is described for the first time. A number of potentially autapomorphic features are identified; however, in common with living elephants and seacows the moerithere periotic is shown to lack the fenestra cochleae and aqueductus cochleae typical of therian mammals. Instead, it possesses a secondarily undivided perilymphatic foramen, a feature considered to be a synapomorphy uniting Proboscidea and Sirenia within the Tethytheria. The supposedly more derived fossil proboscidean, Mimidotherium , along with the primitive fossil sirenian Prorastomus , possess the typical therian pattern of openings to the pars cochlearis of the periotic. It is therefore unclear whether the condition in Recent tethytheres is homologous or independently derived. It is argued that the presence in Moeritherium of a suite of periotic characters more derived than those in Mimidotherium undermines the primitive status of moeritheres relative to numidotheres and all other Proboscidea, and therefore weakens the hypothesis of a secondary reversal to a more primitive auditory region in Numidotheriurn. The biological role of auditory specializations in Recent tethytheres is shown to have been very different, and it is argued that this functional disparity extends to the most primitive members of each order. Demonstrable homoplasy in structure and lack of functional congruence in basal members of both Sirenia and Proboscidea are deemed to be indicative of an independent acquisition of similar structures in the ear region of Recent tethytheres.     

An investigation of the status of the terrestrial slugs Arion ater ater (L.) and Arion ater rufus (L.) (Mollusca, Gastropoda, Pulmonata) in Britain

Three types of evidence, variation in external coloration and patterning. characters of the distal genitalia and biochemical variation, were used to determine if A. a. ater and A. u. rufus could be recognized in Britain. From these studies it was possible to recognize the two taxa, but the variation of the morphological characters was continuous between them. The range of variation, in particular that of the distal genitalia of A. a. ater , was much wider than indicated by previous studies. The biochemical results from the use of zone electrophoresis and staining for non-specific esterases indicated that there was a high level of similarity between the taxa. It was not possible to determine whether the continuity in the variation resulted from hybridization or an overlap between two separate ranges. Consequently, although the results agreed with A. ater being two subspecies, more work is needed both in Britain and on the Continent to extend these observations and to determine the status of the two taxa.     

A new oviraptorid (Dinosauria: Theropoda) from the Upper Cretaceous of Bayan Mandahu,Inner Mongolia

Abstract: A new oviraptorid is described on the basis of a partial forelimb collected from the Upper Cretaceous redbeds of Bayan Mandahu, Inner Mongolia. Machairasaurus leptonychus, gen. et sp. nov. is diagnosed by slender, weakly curved manual unguals, reduced flexor tubercles, penultimate phalanges that are subequal in length to the preceding phalanges, and short, robust manual digits. Machairasaurus is found to be a member of the Ingeniinae, along with Ingenia yanshini, Heyuannia huangi, Conchoraptor gracilis, and Nemegtomaia barsboldi. Machairasaurus exhibits unusual proportions of the manus, suggesting that the manus was not primarily used to grasp prey. Instead, Machairasaurus and other oviraptorids are likely to have fed largely on plant material. The recognition of a previously unknown oviraptorid at Bayan Mandahu provides further evidence that the Bayan Mandahu dinosaur assemblage is distinct from that found at the Djadokhta Formation exposures at Bayn Dzak, Tugriken Shireh, and Ukhaa Tolgod. Given that these localities are separated by just a few hundred kilometres and represent similar palaeoenvironments, marked differences in the fauna suggest that the Bayan Mandahu Formation of Inner Mongolia is not coeval with the known Djadokhta localities in Mongolia.     

Delivery of hatching larvae to estuaries by an amphidromous river shrimp: tests of hypotheses based on larval moulting and distribution

1.  Amphidromous shrimps live and breed in freshwater rivers and streams, but their larvae require development in sea water. Larvae may hatch upstream and then drift to the sea, although in some species females have been reported to migrate to the coast before larvae are released. Here, we tested the relative importance of larval drift and female migration in Macrobrachium ohione (Decapoda: Palaemonidae) in a distributary of the Mississippi River in Louisiana, U.S.A.
2.  Newly hatched (stage-1) larvae are nonfeeding and will not moult to stage 2 (first feeding stage) without encountering salt water. A factorial experiment was conducted in the laboratory to test the effects on moulting to stage 2 of (i) time spent by stage-1 larvae in fresh water before (ii) exposure to and maintenance in water of different salinity. Larvae kept in fresh water for 1 or 3 days before a change to saline water at 6 or 10 ppt showed a greater frequency of moulting than those kept for longer (5 days) in fresh water or changed to less saline water (2 ppt). Non-moulting larvae died or were moribund within 11 days of hatching.
3.  The relative abundance of stage-1 larvae was measured with plankton tows at two locations in the river c. 150 km apart, one near the sea and one upstream. Larval abundances near the sea were significantly greater than those upstream.
4.  The results indicate that hatched larvae of M. ohione have a limited period in which to drift in fresh water before reaching water sufficiently saline to stimulate moulting to the first feeding stage. Female migrations may play an important role in delivering larvae of amphidromous species from large continental river systems in which distances to the sea are great, while larval drift alone may be sufficient in species living in short streams, like those found in many small mountainous tropical islands.