Tomasz Brachaniec

The Lilliput effect in crinoids at the end of the Oceanic Anoxic Event 2: a Case study from Poland

Abstract. The Cretaceous Period (145–66 Ma) consisted of several oceanic anoxic events (120–80 Ma), stimulated by global greenhouse effects. The Oceanic Anoxic Event 2 (OAE2) occurred worldwide from the late Cenomanian to the early-middle Turonian, causing a significant faunal turnover, mostly in marine biota, pushing some species to the brink of extinction. Some organisms also underwent morphological changes, including reduction in size. This anoxic event drove other changes—e.g., in habitats or strategy of life. We show that stalkless crinoids (comatulids) from the Turonian of Poland adapted to unfavorable environmental conditions by reducing their body size. Furthermore, at the moment when environmental factors became favorable again, these crinoids regained their regular (pre-event) size. This phenomenon likely illustrates the so-called dwarfing mode of the Lilliput effect.

Ophiuroids discovered in the middle triassic hypersaline environment.

Echinoderms have long been considered to be one of the animal phyla that is strictly marine. However, there is growing evidence that some recent species may live in either brackish or hypersaline environments. Surprisingly, discoveries of fossil echinoderms in non-(open)marine paleoenvironments are lacking. In Wojkowice Quarry (Southern Poland), sediments of lowermost part of the Middle Triassic are exposed. In limestone layer with cellular structures and pseudomorphs after gypsum, two dense accumulations of articulated ophiuroids (Aspiduriella similis (Eck)) were documented. The sediments with ophiuroids were formed in environment of increased salinity waters as suggested by paleontological, sedimentological, petrographical and geochemical data. Discovery of Triassic hypersaline ophiuroids invalidates the paleontological assumption that fossil echinoderms are indicators of fully marine conditions. Thus caution needs to be taken when using fossil echinoderms in paleoenvironmental reconstructions.

Putative Late Ordovician land plants

The colonization of early terrestrial ecosystems by embryophytes (i.e. land plants) irreversibly changed global biogeochemical cycles (Berner & Kothavala, 2001; Berner et al., 2007; Song et al., 2012). However, when and how the process of plant terrestrialization took place is still intensely debated (Kenrick & Crane, 1997; Kenrick et al., 2012; Edwards et al., 2014; Edwards & Kenrick, 2015). Current knowledge suggests that the earliest land plants evolved from charophycean green algae (Karol et al., 2001) most probably during Early-Middle Ordovician times (Rubinstein et al., 2010; and references cited therein). They were represented by small nonvascular bryophyte-like organisms (Edwards & Wellman, 2001;Wellman et al., 2003; Kenrick et al., 2012). The oldest fossil evidence from dispersed spores of presumable bryophytic nature is known from aMiddle Ordovician locality (c. 470million years ago (Ma), Rubinstein et al., 2010; Fig. 1) from Argentina (Gondwana palaeocontinent). The dispersed spore fossil record also suggests that the first radiation of vascular plants probably occurred during Late Ordovician times (c. 450Ma, Steemans et al., 2009). However, unequivocal macrofossils of vascular plants appear much later, during mid-Silurian (c. 430Ma, Edwards et al., 1992). This macrofossil evidence comes from the fossil-genus Cooksonia, an early polysporangiophyte (i.e. a plant with bifurcating axes and more than one sporangium), which is considered the earliest vascular land plant (Edwards et al., 1992; Fig. 1). Further advances in knowledge about the origin and early dispersion of polysporangiophytes are needed for a better understanding of the initial plant diversification. Unfortunately, unravelling the initial steps of polysporangiophyte evolution is hindered by gaps in the fossil record of the earliest plants as well as by limitations of inference based on molecular clocks (Kenrick et al., 2012; Edwards & Kenrick, 2015). Assessing the affinities of fragmentary fossils is frequently only tentative. Most often, only partial evidence for land plant nature is visible on fossils of Silurian–Devonian age. Nevertheless, there are numerous examples in the deep-time fossil record of organisms that have been interpreted as early embryophytes even though unambiguous land plant characters were not demonstrated. For instance, Edwards & Feehan (1980) reported on some Silurian terminal sporangia and dichotomous axes interpreted as Cooksonia-type plantswith no evidence for in situ spores nor for tracheids.Wellman et al. (2003) described the first plant mesofossils with in situ spores from the Ordovician (Katian) fossil record, but the morphology of the parent plants remains unknown. More recently, Morris et al. (2011) reported on numerous fragments of LowerDevonian plants with terminal sporangia and dichotomous axes, some of them lacking preserved unambiguous land plant characters. Interestingly, some of the plants illustrated by Morris et al. (2011, pl. VI) appear closely similar to those reported in Fig. 2 (see later). Here, we document an Ordovician (Hirnantian, c. 445Ma) putative plant macrofossil assemblage. The specimens come from an Upper Ordovician locality at Zbrza in the southern Holy Cross Mountains (HCM, central Poland, SW peri-Baltica; Supporting Information Figs S1, S2, see also Notes S1). The fossils occur in mudstones of the uppermost Ordovician (Hirnantian) Zalesie Formation dated by trilobites, brachiopods and palynomorphs (Kielan, 1959; Temple, 1965; Masiak et al., 2003; Trela & Szczepanik, 2009). The age of the plant-bearing sediments is confirmed by acritarchs and chitinozoans (Notes S1). Reported evidence consists of dichotomously branched slender axes, some with terminal discoid or ovoid structures interpreted as sporangia, which could represent the earliest macrofossil occurrence of polysporangiophytes (Fig. 1). The plant fossils described herein are scattered among various fragments of coalifiedmaterial. Two branching axes broken at both ends (3 mm long9 0.1 mm wide and 2 mm long9 0.3 mm wide, respectively; Fig. 2a,b) are attributable to the fossil genusHostinella that includes vegetative isotomously branched axes. Another specimen shows a trichotomous axis division (3.2 mm long9 0.3 mm wide; Fig. 2c), a feature known to occur in some late Silurian–early Devonian plants (Gonez & Gerrienne, 2010a, b). The studied samples also yielded several probably fertile axes. A small, dichotomously branched, slender and leafless stem (1.5 mm long9 0.2 mmwide; Fig. 2d) bears terminal structures interpreted as sporangia (0.4 mm long9 0.3 mm wide; Fig. 2d). The two other fertile specimens are not branched.They consist of a short axis (1.1 mm long9 0.3 mm wide; Fig. 2e) ending either in a horizontally stretched, presumably cup-shaped, structure interpreted as a sporangium (0.8 mm long9 1.1 mm wide; Fig. 2e) or in an ovoid/hemispherical sporangium-like body (1.3 mm long9 1 mm wide; Fig. 2f). Their form, size and structure seem to be close to those observed fromCooksonia pertoni (Fig. 2e; Lang, 1937; Edwards & Feehan, 1980) and C. hemisphaerica (Fig. 2f; Edwards & Rogerson, 1979; Edwards & Feehan, 1980), respectively. Moreover, the specimen illustrated in Fig. 2(d) looks quite similar to the bifurcating axis showing the basal part of a sporangium described by Edwards et al. (2014, Fig. 3f). Within a macerated residue, we found rare trilete spores resembling the Ambitisporites avitus-dilutus (Steemans et al., 1996; Fig. 2g,h), a morphon interpreted as indicative of vascular plants (Fanning et al., 1988; Steemans et al., 2009); however the trilete marks of our specimens are not regularly formed, which casts doubts on their trilete spore nature. Interestingly, there are a variety of Ordovician spores with irregular trilete-like folds, such as Besselia nunaatica (Nøhr-Hansen & Koppelhus, 1988) that are well known from mosses and hornworts. The last important feature shown by our

Echinoid Bite Traces on Late Cretaceous (Early Maastrichtian) Sea Lilies from Southern Poland

Abstract. Echinoid bite traces on Late Cretaceous (early Maastrichtian) bourgueticrinids and isocrinids of southern Poland (Miechów Trough) were documented. The bitten sea lilies co-occurred with Goniopygus, a regular echinoid possessing an Aristotles lantern. This is the first record of Goniopygus in the lower Maastrichtian of Poland. Considering former studies, as well as direct in situ observations of extant sea lilies and sea urchin behavior, the traces at hand could be most likely linked with predatory actions of the Goniopygus echinoid. Such studies on predatory phenomena are crucial and could provide baseline data concerning the evolutionary trends among organisms engaged in the “arms race”.

Troglomorphism in the middle Triassic crinoids from Poland

In this paper, we document the Middle Triassic marine fauna recovered from the fissure/cave system of Stare Gliny (southern Poland) developed in the Devonian host dolomite. The fossils are mostly represented by in situ preserved and small-sized holdfasts of crinoids (Crinoidea) that are attached to the cave walls. Other fossils found in the cave infills include articulated brittle stars and brachiopods. Our findings constitute the oldest Mesozoic evidence for troglophile crinoids. We suggest that troglomorphism in these echinoderms was likely related to protection against predation, which underscores the magnitude of anti-predatory adaptations to increased predation pressure that occurred during the Early Mesozoic Marine Revolution.

Anti-predator adaptations in a great scallop (Pecten maximus) – a palaeontological perspective

Abstract Shelly fauna was exposed to increased pressure exerted by shell-crushing durophagous predators during the so-called Mesozoic Marine Revolution that was initiated in the Triassic. As a result of evolutionary ‘arms race’, prey animals such as bivalves, developed many adaptations to reduce predation pressure (e.g. they changed lifestyle and shell morphology in order to increase their mechanical strength). For instance, it was suggested that Pectinidae had acquired the ability to actively swim to avoid predator attack during the early Mesozoic. However, pectinids are also know to have a specific shell microstructure that may effectively protect them against predators. For instance, we highlight that the shells of some recent pectinid species (e.g. Pecten maximus) that display cross-lamellar structures in the middle part playing a significant role in the energy dissipation, improve the mechanical strength. In contrast, the outer layers of these bivalves are highly porous, which allow them to swim more efficiently by reducing the shell weight. Pectinids are thus perfect examples of animals optimising their skeletons for several functions. We suggest that such an optimisation of their skeletons for multiple functions likely occurred as a results of increased predation pressure during the so-called Mesozoic Marine Revolution.

The large superpredators’ teeth from Middle Triassic of Poland

ABSTRACT An unusual large teeth, finding from time to time in marine sediments of Muschelkalk, Silesia, Poland indicate the superpredators occurrence. According to size and morphological features the teeth are similar to archosaurs or giant marine reptiles.

Possible vertebrate coprolites from the Upper Cretaceous (Coniacian) of the Sudetes Mountains (southern Poland)

Possible coprolites from the Upper Cretaceous (Coniacian) of Waliszow Stary in the Sudetes Mountains (southern Poland) are described for the first time. They are relatively small, irregular in outline, and preserved as goethite, limonite, siderite and hematite. Although it is difficult to identify the producer of these coprolites, they were most probably formed by some fish.

Environmental control on shell size of Middle Triassic bivalve Plagiostoma

Fossil shells of the marine bivalve Plagiostoma striatum Schlotheim sampled from the Middle Triassic (so-called Muschelkalk) of Poland demonstrate that, under unfavourable environmental conditions, this species commonly occurring in Triassic German basins exhibits a dwarfed shell. As a consequence of a marine regression episode resulting in a significant increase of salinity and a partial emersion of seafloor these bivalves vanished. The next transgressive pulse caused a re-emergence of these bivalves. They were initially characterized by half-size shells than in the population living prior to the regression episode and, subsequently, during progressive transgression, their shells returned to normal size. Coincidence between eustatic curve and changes in bivalve shell size and their disappearance may be attributed also to biotic interactions, such as a biotic collapse in primary bioproductivity or/and a competition for space or any other resources due to shelf habitat loss during regressive periods.

Shock structures in the Morasko meteorite - preliminary SEM data

Abstract This paper is a preliminary review of main shock deformations in the Morasko meteorite. Three main types of metamorphism structures occur in the investigated material: (i) brittle, (ii) plastic and (iii) thermal. Their interpretation may indicate, that Morasko meteorite reveals several stages of shock, eg.: extraterrestrial collisions and fall on the Earth