Gill structure and relationships of the Triassic cycloid crustaceans

Osteology of a forelimb of an aetosaur Stagonolepis olenkae (Archosauria: Pseudosuchia: Aetosauria) from the Krasiejów locality in Poland and its probable adaptations for a scratch-digging behavior

Aetosaurs are armored basal archosaurs that played a significant role in land ecosystems during the Late Triassic (237–201 Ma). The polish species Stagonolepis olenkae Sulej, 2010 described from the Krasiejów locality (southern Poland) is one of the oldest known representatives of the group. Abundant and well-preserved material, including partially articulated specimens, allows a detailed description of the forelimbs in this species. The forelimbs of S. olenkae are the most similar to that of large aetosaurs like Desmatosuchus smalli, Desmatosuchus spurensis, Longosuchus meadei, Typothorax coccinarum or Stagonolepis robertsoni. Several characters recognized in the forelimbs of S. olenkae suggest its adaptation for scratch-digging. The most salient of these features are: short forearm, carpus, and hands, with the radius shorter than the humerus, carpus and manus shorter than the radius (excluding terminal phalanges); a prominent deltopectoral crest that extends distally on the humerus and a wide prominent entepicondyle, a long olecranon process with well-marked attachment of triceps muscle; hooked, laterally compressed, claw-like terminal phalanges with ornamentation of small pits (indicative of well-developed keratin sheaths). S. olenkae might have used its robust forelimbs to break through the compacted soil with its claws and proceed to dig in search of food in softened substrate with the shovel-like expansion at the tip of its snout. The entire forelimb of S. olenkae is covered by osteoderms, including the dorsal surface of the hand, which is unusual among aetosaurs and have not been noted for any species up to date.

Cranial bone histology of Metoposaurus krasiejowensis (Amphibia, Temnospondyli) from the Late Triassic of Poland

In this study, 21 skull bones of Metoposaurus krasiejowensis from the Late Triassic of Poland were investigated histologically. Dermal bones show a diploë structure, with an ornamented external surface. The ridges consist of mostly well vascularized parallel-fibered bone; the valleys are built of an avascular layer of lamellar bone. The thick middle region consists of cancellous bone, with varying porosity. The thin and less vascularized internal cortex consists of parallel-fibered bone. The numerous Sharpey's fibers and ISF are present in all bones. The cyclicity of growth is manifested as an alternation of thick, avascular annuli and high vascularized zones as well as a sequence of resting lines. The detailed histological framework of dermal bones varies even within a single bone; this seems to be related to the local biomechanical loading of the particular part of the skull. The dynamic processes observed during the ornamentation creation indicate that the positions of the ridges and grooves change during growth and could be a specific adaptation to changing biomechanical conditions and stress distribution during bone development. In the supratemporal, the cementing lines show that the remodeling process could be involved in the creations of sculpture. The common occurrence of ISF suggests that metaplastic ossification plays an important role during cranial development. Endochondral bones preserved the numerous remains of calcified cartilage. This indicates that ossification follows a pattern known for stereospondyl intercentra, with relatively slow ossification of the trabecular part and late development of the periosteal cortex. The large accumulation of Sharpey's fibers in the occipital condyles indicates the presence of strong muscles and ligaments connecting the skull to the vertebral column.

Identification and characterisation of hemocyanin of the fish louse Argulus (Crustacea: Branchiura)

Hemocyanin transports oxygen in the hemolymph of many arthropod species. Within the crustaceans, this copper-containing protein was thought to be restricted to Malacostraca, while other crustacean classes were assumed to employ hemoglobin or lack any respiratory protein. Only recently it has become evident that hemocyanins also occur in Remipedia and Ostracoda. Here we report for the first time the identification and characterisation of hemocyanin in the fish louse Argulus, which belongs to the class of Branchiura. This finding indicates that hemocyanin was the principal oxygen carrier in the stem lineage of the pancrustaceans, but has been lost independently multiple times in crustacean taxa. We obtained the full-length cDNA sequences of two hemocyanin subunits of Argulus foliaceus by a combination of RT-PCR, RACE and Illumina sequencing of the transcriptome. In addition, one full-length and one partial cDNA sequence were derived from the transcriptome data of Argulus siamensis. Western blot analysis confirmed the presence of at least two hemocyanin subunits in A. foliaceus, which are expressed at the mRNA level at a 1:3.5 ratio. The addition to the branchiuran hemocyanin subunits to a multiple sequence alignment of arthropod, hemocyanins improved the phylogenetic resolution within the pancrustacean hemocyanins. Malacostracan, ostracod and branchiuran hemocyanins are distinct from the hexapod and remipede hemocyanins, reinforcing the hypothesis of a close relationship of Remipedia and Hexapoda. Notably, the ostracod hemocyanins are paraphyletic with respect to the branchiuran hemocyanins, indicating ancient divergence and differential loss of distinct subunit types.