Wyniki wyszukiwania - Biblioteka Nauki

1

A Marrella-like arthropod from Cambrian of Australia: A new link between "Orsten"-type and Burgess Shale assemblages

100%

Haug J. T. , Castellani C. , Haug C. , Waloszek D. , Maas A.

|

nr 3

EN

An isolated exopod in uncompressed three−dimensional “Orsten”−type preservation from the Cambrian of Australia represents a new species of Marrellomorpha, Austromarrella klausmuelleri gen. et sp. nov. The exopod is composed of at least 17 annuli. Each of the proximal annuli carries a pair of lamellae: one lamella on the lateral side and one on the median side. The distal annuli bear stout spines in the corresponding position instead of lamellae, most likely representing early ontogenetic equivalents of the lamellae. The new find extends the geographical range of the taxon Marrellomorpha. Additionally, it offers a partial view into marrellomorph ontogeny. The occurrence of a marrellomorph fragment in “Orsten”−type preservation provides new palaeo−ecological insights into the possible connections between the “Orsten” biotas and other fossil Lagerstätten. Finding such connections is necessary for understanding the complex ecosystems of early Palaeozoic times.

2

Biologia owadów

100%

Krzeminska A.

|

nr 2

3

A new species of rust fungi from the middle Eocene Sakhalinian amber

100%

Tykhonenko Y. , Hayova V. , Ignatov M. , Vasilenko D. , Perkovsky E. E.

|

nr 4

4

Soft-part preservation in two species of the arthropod Isoxys from the middle Cambrian Burgess Shale of British Columbia, Canada

80%

Garcia-Bellido D. C. , Vannier J. , Collins D.

|

nr 4

EN

More than forty specimens from the middle Cambrian Burgess Shale reveal the detailed anatomy of Isoxys, a worldwide distributed bivalved arthropod represented here by two species, namely Isoxys acutangulus and Isoxys longissimus. I. acutangulus had a non−mineralized headshield with lateral pleural folds (= “valves” of previous authors) that covered the animal’s body almost entirely, large frontal spherical eyes and a pair of uniramous prehensile appendages bearing stout spiny outgrowths along their anterior margins. The 13 following appendages had a uniform biramous design—i.e., a short endopod and a paddle−like exopod fringed with marginal setae with a probable natatory function. The trunk ended with a flap−like telson that protruded beyond the posterior margin of the headshield. The gut of I. acutangulus was tube−like, running from mouth to telson, and was flanked with numerous 3D−preserved bulbous, paired features interpreted as digestive glands. The appendage design of I. acutangulus indicates that the animal was a swimmer and a visual predator living off−bottom. The general anatomy of Isoxys longissimus was similar to that of I. acutangulus although less information is available on the exact shape of its appendages and visual organs. I. longissimus is characterized by extremely long anterior and posterior spines. There are now seven Isoxys species known with soft−part preservation, I. acutangulus, I. longissimus from the Burgess Shale, I. auritus and I. curvirostratus from the Maotianshan Shale of China, I. communis and I. glaessneri from the Emu Bay Shale of Australia and I. volucrisfrom Sirius Passet in Greenland. The frontal appendages of Isoxys strongly resemble those of other Cambrian arthropods, characterized by a single pair of “great appendages” with a shared prehensile function yet some variability in length and shape.

5

A new leanchoiliid megacheiran arthropod from the lower Cambrian Emu Bay Shale, South Australia

80%

Edgecombe G. D. , Garcia-Bellido D. C. , Paterson J. R.

|

nr 2

EN

The Leanchoiliidae is well−known from abundant material of Leanchoilia, from the Burgess Shale and Chengjiang Konservat−Lagerstätten. The first Australian member of the group is Oestokerkus megacholix gen. et sp. nov., described from the Emu Bay Shale (Cambrian Series 2, Stage 4), at Buck Quarry, Kangaroo Island, South Australia, and is intermediate in age between the well known leanchoiliid species from the Burgess Shale and Chengjiang. Phylogenetic analysis of “short great appendage” arthropods (Megacheira) in the context of the chelicerate stem group resolves the Australian species as sister to Burgess Shale, Utah, and Chengjiang Leanchoilia species, but most readily distinguished from Leanchoilia and Alalcomenaeus by a different telson shape, interpreted as being forked, widening distally, and with a few dorsally curved spines at the posterior angle. Leanchoiliid interrelationships are stable to alternative character weights, and Megacheira corresponds to a clade in most analyses.

6

Arthropod trace fossils from Eocene cold climate continental strata of King George Island, West Antarctica

80%

Uchman A. , Gazdzicki A. , Blazejowski B.

|

nr 2

EN

Siltstone and sandstone beds of the Mount Wawel Formation (Eocene) contain trace fossils interpreted as insect resting traces and arthropod trackways, the latest determined as Glaciichnium australis isp. nov. and cf. Pterichnus isp. Glaciichnium is included in a new ichnofamily Protichnidae, which embraces invertebrate trackways composed of straight central trail(s) and lateral tracks. The same deposits contain fragments of plant stems in growth position, delicate fern-like plant twigs and leaves of Nothofagus. Their deposition took place in very shallow but flowing water, probably in a marginal part of a lake, perhaps in a delta. The presence of mudcracks proves incidental exposure of the sediment. The trace fossils were produced by arthropods, especially insects and/or isopods, between episodes of deposition and were influenced by the water flow and subtle changes in substrate consistency. This resulted in several morphological variants of the traces. Glaciichnium australis is similar to those produced by some caddisflies (Trichoptera) in shallow puddles in the Tatra Mountains of Poland. The arthropod-dominated trace fossil assemblage is similar to the Glaciichnium ichnocoenosis, which is known from some Pleistocene lacustrine varve sediments of Europe. This fits well with the beginning of climatic cooling in Antarctica during the late Eocene. This also shows the recurrence of some ichnological features on both ends of the globe in similar palaeoenvironmental conditions and supports basics of the ichnofacies concept.

7

A new euarthropod from the Cambrian Stage 4 Guanshan Biota of South China

80%

Jiao D.-G. , Du K.-S.

|

tom 67

|

nr 4

8

Regional and local faunas of parasitic Hymenoptera

80%

Urlich W.

|

nr 3

9

Morphological requirements in limulid and decapod gills: A case study in deducing the function of lamellipedian exopod lamellae

80%

Suzuki Y. , Kondo A. , Bergstrom J.

|

nr 2

EN

According to one hypothesis, the exopods of extinct lamellipedian arthropods functioned as gills. To evaluate this hypothesis, the growth rates in Limulus polyphemus for total gill surface, average area per single gill lamella and number of gill lamellae are documented. The rates are compared with corresponding rates in decapod crustaceans in order to make deductions on morphological constraints in multi−foliated gills. The growth rates are given as allometric scaling exponents relative to the animal dry−body weight. The comparisons reveal that each allometric exponent is similar among examined species irrespective of differences in gill morphology or animal body plans. The numerical growth of lamellae obviously is much smaller than the growth of the total respiratory surface. To fulfill these trends in multi−foliated gills, the overall profile tends to become conical, with the result that the surface area is a couple of magnitudes larger at the base of the cone than at the tip. This geometrical shape appears to keep the numerical value of the total respiratory area (total lamellar surface) proportional to the cube of the total number of lamellae. The situation is entirely different in animals with lamellipedian exopods. In the latter, lamellae are slender structures carried in a straight row and, as exemplified by Naraoia, their increase in number during the growth is only half that required for the exopod lamellae to have functioned as an arthropod multi−foliated gill cone.

10

A large xenusiid lobopod with complex appendages from the Lower Cambrian Chengjiang Lagerstatte

80%

Liu J. , Shu D. , Han J. , Zhang Z. , Zhang X.

|

tom 51

|

nr 2

EN

A large lobopod, Jianshanopodia decora gen. et sp. nov., with body length (excluding appendages) about 220 mm from the Lower Cambrian Haikou section, near Kunming, Yunnan, southwest China, shows a mixture of characters, including features of the lobopod Xenusion Pompeckj, 1927, e.g., a large cylindrical body with annulations, stout and strong lobopod appendages each bearing bases of serial tubercles, and of Aysheaia Walcott, 1911, i.e., a pair of large frontal appendages. This suggests that the new genus might be a connecting link between Xenusion and Aysheaia. Besides, Jianshanopodia shares some features with the Early Cambrian stem group arthropod Pambdelurion Budd, 1997, and Kerygmachela Budd, 1993, e.g., the pairs of mid−gut diverticula, the possible presence of tail fan, the mouth cone, the frontal pharyngeal structures and the pharynax are surrounded by the bases of the large frontal appendages. However, compared with a series of segmentally arranged, imbricating, paddle−shaped, movable lateral flaps of both Pambdelurion and Kerygmachela, Jianshanopodia possesses distinct complex appendages with tree−like or lamellate branches. The discovery of this rare transitional form not only throws new light on the early diversification of lobopods, and may also have significance with respect to the origin of arthropods.