Błażej Błażejowski

The horseshoe crab of the genus Limulus: living fossil or stabilomorph?

A new horseshoe crab species, Limulus darwini, is described from the uppermost Jurassic (ca. 148 Ma) near-shore sediments of the Kcynia Formation, central Poland. The only extant species Limulus polyphemus (Linnaeus) inhabits brackish-marine, shallow water environments of the east coast of the United States. Here it is shown that there are no important morphological differences between the Kcynia Formation specimens and extant juvenile representatives of the genus Limulus. The palaeoecological setting inhabited by the new species and the trophic relationships of extant horseshoe crabs are discussed in an attempt to determine the potential range of food items ingested by these Mesozoic xiphosurans. In this paper we propose the adoption of a new term stabilomorphism, this being: an effect of a specific formula of adaptative strategy among organisms whose taxonomic status does not exceed genus-level. A high effectiveness of adaptation significantly reduces the need for differentiated phenotypic variants in response to environmental changes and provides for long-term evolutionary success.

X-ray Microtomography (XMT) of Fossil Brachiopod Shell Interiors for Taxonomy

The ability to see and understand the three-dimensional structure of an investigated object plays a key role in studying fossil remains. All living organisms are formed in three-dimensions, but unfortunately fossilization processes often reduce overall shape, making it difficult to gather information about real overall appearance, functionality, and inner structure. Here, using a specimen of the brachiopod Tere bratula terebratula we demonstrate a non-destructive technique for exploring the 3-D internal structure of fossil remains. The use of tomography allows the construction of a set of transverse serial sections in the manner used by brachiopod researchers for decades.

A moment from before 365 Ma frozen in time and space

This study presents a detailed analysis of an exceptionally well-preserved articulated specimen of the trilobite Trimerocephalus from the Late Devonian of the Holy Cross Mountains in Poland. X-ray microtomography reveals the oldest direct evidence for a moulting episode known from the fossil record. The process of moulting as well as associated features observed in the investigated specimen are interpreted by comparison with extinct and extant Xiphosurida arthropods, which survived global P/T extinction and are among the closest extant relatives of trilobites. A very special moment frozen in time and space millions years ago provides rare insights into the behavior and physiology of these long-extinct arthropods.

The Oldest Species of the Genus Limulus from the Late Jurassic of Poland

This paper describes the discovery of new, exceptionally well preserved Late Jurassic (Late Tithonian) horseshoe crabs belonging to the genus Limulus, which are considered to be the oldest known representatives of the genus. The three-dimensionally preserved fossil horseshoe crabs, belonging to two species: Limulus darwini and Crenatolimulus sp. nov., recently were discovered in the Owadow-Brzezinki Quarry in Central Poland. The state of preservation of the fossil horseshoe crabs is described and the evolutionary lineage of both extinct and extant limulids is discussed. The palaeoenvironment inhabited by the new species and the trophic relationships of living horseshoe crabs are investigated in an attempt to determine the potential relationships between Mesozoic and recent xiphosurans.

Lower Permian Bryozoans from Southern and Central Spitsbergen, Svalbard

Bryozoans from the Lower Permian Treskelodden and Wordiekammen formations of southern and central Spitsbergen respectively, Svalbard, have been studied. Twenty species are identified, including one new genus, Toulapora gen. nov., with Toulapora svalbardense as type species and one new species, Ascopora birkenmajeri sp. nov. The taxonomic composition is typical Lower Permian, with species in common with Timan-Pechora and the Urals (Russia) and Ellesmere Island (the Canadian Arctic). Growth habits reflect a moderately to deeper shelf environment.

Limulitella tejraensis, a new species of limulid (Chelicerata, Xiphosura) from the Middle Triassic of southern Tunisia (Saharan Platform)

Abstract. Numerous well-preserved remains of a new limulid species from the Anisian-lower Ladinian (Middle Triassic) of the Tejra section of southern Tunisia are described. Comparisons are made with limulids from the Triassic deposits of Europe and Australia. The new specimens are congeneric with the type species of Limulitella, but show some morphological differences. Here we describe Limulitella tejraensis new species, a small limulid with semicircular prosoma, small and triangular opisthosoma, well-defined axial ridge, and pleurae along both ridges of the opisthosoma. The Tunisian Limulitella fossils are associated with conchostracans, bivalves, gastropods, and microconchids. Sedimentological and paleontological data from the Tejra section suggest freshwater to brackishwater conditions during the formation of the fossil-bearing interval and the influence of marine transgression into a playa-like environment. Supposed adaptation to the stressful environment sheds new light on the origin and survival of the extant limulines. This is the first report of limulid body fossils from the Triassic of North Africa and the first documentation of Limulitella in the Middle Triassic of northern Gondwanaland.

Late Jurassic jaw bones of Halecomorph fish (Actinopterygii: Halecomorphi) studied with X-ray microcomputed tomography

New finds of Halecomorphi fish remains from Late Jurassic limestones of Owadów-Brzezinki (Poland) are investigated using X-ray microcomputed tomography (XMT) revealing details of jaw bones for actinopterygian fish histology. Three-dimensional (3-D) reconstruction allows for correct taxonomical verification. The possibility of 3-D printing gives the opportunity for work with a model in any desired scale without risk of damaging the specimen. Błażej Błażejowski. Institute of Paleobiology, Polish Academy of Sciences, Twarda 51/55, 00-818 Warszawa, Poland. bblazej@twarda.pan.pl Paul Lambers. Universiteitsmuseum Utrecht, Lange Nieuwstraat 106, 3512 PN Utrecht, The Netherlands, p.h.lambers@uu.nl Piotr Gieszcz. Independent Center for Advanced Research machinic.it, Stawki 4c/10, 00-193 Warszawa, Poland, pjogi@interia.eu Daniel Tyborowski. Museum and Institute of Zoology, Polish Academy of Sciences, Wilcza 64, 00-679 Warszawa, Poland, d.tyborowski@student.uw.edu.pl Marcin Binkowski. Department of Computer Science and Materials Science, University of Silesia, Katowice, Poland, marcin.binkowski@us.edu.pl