Osteological fossils of dinosaurs are relatively rare in the Late Triassic and Early Jurassic. Thus, ichnofossils are a critical source of information on Late Triassic terrestrial vertebrate communities. The outcrops of the Tomanová Formation (?late Norian—Rhaetian) in the Tatra Mountains of Poland and Slovakia have yielded a diverse ichnofauna. Seven more or less distinct morphotypes of dinosaur tracks have been recognized and are discussed. Most tracks are partly eroded or deformed, but are preserved well enough to be assigned to a range of trackmakers, including early ornithischians, small and large theropods (coelophysoids and/or possibly early tetanurans), and probably basal sauropodomorphs (“prosauropods”) or first true sauropods.
Trackways, footprints and coprolites are the most common vertebrate fossils and provide unparalleled information about the behavior of terrestrial vertebrates in the environments in which they lived (Lockley 1998). One of the aims of ichnological research is the reconstruction of the animal communities represented by the trace fossils. However, in the case of vertebrates in particular, such reconstruction can be fraught with difficulties, mostly due to problems with identifying the trackmakers and their relative abundance.
Studies of the Late Triassic ichnofauna illustrate some of these difficulties (see Olsen et al. 1998, 2002), but these are also critical fossils to consider when studying faunal change during the Late Triassic, an interval marked by evolutionary radiations, climate change, and supposed mass extinctions (see Brusatte et al. 2008). The information that can be inferred from Late Triassic ichnofaunas is particularly vital for our understanding of dinosaur ecology because of the scarcity of skeletal remains of Late Triassic members of this iconic group (see Langer and Benton 2006; Nesbitt et al. 2007; Brusatte et al. 2008; Langer et al. 2010).
This paper presents a description of the Late Triassic dinosaur track assemblages from the Tatra Mountains of Poland and Slovakia (Fig. 1). This overview includes the revision of published and previously unpublished material (housed in the Museum of the Tatra Mountains National Park in Tatranská Lomnica, Slovakia; Slovak National Museum, Bratislava, Slovakia and Nature Museum of the Tatra Mountains National Park, Zakopane, Poland), and is based upon both data generated from existing collections and in situ measurements of additional material that has recently been discovered during new fieldwork (Figs. 2A, B, 3A, B—E, 4B, C, 5, 6). This fieldwork was part of the revision of Carboniferous—Cretaceous tetrapod tracks in Poland by a group of researchers from the Department of Paleobiology and Evolution of the University of Warsaw (Warsaw, Poland), the Institute of Paleobiology, Polish Academy of Sciences (Warsaw, Poland) and the Geological Museum, Polish Geological Institute (Warsaw, Poland).
The first dinosaur tracks reported from the Tatra Mountains were discovered in the Tomanová Formation, on the southern slope of Czerwone Wierchy in Cicha Valley, in the Červený Ŭplaz region of Slovakia (Fig. 1). These tracks were found by Jozef Michalík and described by Michalík et al. (1976). Those authors proposed a new ichnospecies, Coelurosaurichnus tatricus, for three tridactyl ichnites preserved on one sandstone slab (specimen numbers Z 14 296—paratype and Z 14 297—holotype, Slovak National Museum, Bratislava). Later, Michalík and Kundrát (1998) redescribed these ichnites and suggested that they could be referred to the ichnogenus Eubrontes Hitchcock, 1845, an ichnotaxon that is characteristic of the Early Jurassic dinosaur ichnoassemblages from North America, Europe and South Africa (Olsen and Galton 1984; Olsen et al. 1998; Lockley and Meyer 2000). Large tridactyl theropod tracks discovered in Cicha Valley were also revised by Gierliński and Sabath (2005) and Lucas et al. (2006). According to Gierliński and Sabath (2005) these tracks are assignable to Eubrontes and are associated in the Tatra Mountains tetrapod ichnoassemblage with characteristic Triassic ichnogenera: “Tetrasauropus” (= Eosauropus, Lockley et al. 2006) and “Pseudotetrasauropus” (= Evazoum, Nicosia and Loi, 2003; = Brachychirotherium, Klein et al. 2006). Both proposals have not been confirmed by the study presented here.
Nearly thirty years later, new footprints were discovered in the Late Triassic fluvial deposits of the Tatra Mountains (Niedźwiedzki 2005, 2008; Niedźwiedzki and Sulej 2007). In September 2004, three dinosaur footprints were found at Czerwone Żlebki, in the Polish Western Tatra Mountains (Fig. 1). Two specimens were found in the talus slope (Fig. 2C, D) and the third (Fig. 4E) was found in situ in the middle part of an exposed lithological profile. Other material was discovered in 2006 and 2007 during short field investigations in the Polish and Slovakian parts of the Tatra Mountains. These tracks came from two sites (Czerwone Żlebki and Červený Ŭplaz, Western Tatra Mountains; Fig. 1) where the strata of the Tomanová Formation are well exposed.
The new footprints represent pedal ichnites of theropod dinosaurs (cf. Kayentapus isp., Anchisauripus isp., cf. Grallator isp.; Figs. 3–5) and possible ornithischian dinosaurs (cf. Anomoepus isp., ?cf. Moyenisauropus isp.; Fig. 2). There are also enigmatic large circular and oval structures, probably made by an early sauropodomorphs (Fig. 6), and a large tridactyl ichnite (described in this paper as cf. Eubrontes isp.), probably theropod in origin (Fig. 5). These new paleoichnological finds are important for understanding the ichnodiversity and ichnotaxonomy of latest Triassic (?Norian—Rhaetian) vertebrate assemblages (especially dinosaur assemblages), and may bear on the patterns of faunal change associated with the radiation and early evolution of dinosaurs.
Near the end of the Triassic period, following the depositions of the characteristic Alpine Keuper facies, typical continental conditions developed in the High-Tatric Basin, resulting in the formation of fresh-water organic-rich black shales with macrofloral remains (Raciborski 1890) and sphaerolitic ironore nodules (Radwański 1968; Nejbert and Jurewicz 2004). These strata, which include the Tomanová Formation, have been studied for more than 100 years; important works include Raciborski (1890), Uhlig (1897), Kuźniar (1913), Rabowski (1925, 1959), Turnau-Morawska (1953), Kotański (1956, 1959a–c, 1961), Gorek (1958), Radwański (1968), Michalík (1978, 1980), and Michalík et al. (1976, 1988). The Tomanová Formation is usually assigned a Rhaetian age (Jurewicz 2005). Under the lithostratigraphic scheme of Raciborski (1890), the “Tomanová layers” included the whole clastic complex of diverse sediments of various colors. Uhlig (1897) divided this complex into lower-beds (so-called “varicolored”) classified as Keuper, and upper dark brown/ black-colored beds of Rhaetian age. According to Uhling (1897), only the upper, dark brown part of the complex was designated as the “Tomanová layer”.
Plant fossils from the upper part of the assemblage, described by Raciborski (1890), were interpreted as Rhaetian in age (Lepidopteris floral assemblage). Macrofloral fossils from the Tomanová Formation were unfortunately not the subject of detailed research by Reymanówna (1984) and Michalík et al. (1988).
A similar division of the clastic complex of the “Tomanová layer” was proposed by Kotański (1959b, c, 1961). The lower complex (“varicolored”), distinguished and classified by Uhlig (1897) as Keuper strata, was referred to as Rhaetian by Kotański (1956).
In addition, on the basis of the continuity of sedimentation between the Norian/Rhaetian complexes (noticed previously by Uhlig 1897), it was assumed that the “Tomanová layers” (sensu Uhlig 1897) may partially represent Norian deposits (Kotański 1959b, c, 1961). This assumption is not in contradiction to the macrofloral record. A Rhaetian macroflora, described by Raciborski (1890), originates from the upper part of the deposits of the Tomanová Formation. Slovakian researchers consider these deposits as Norian—Rhaetian. Michalík et al. (1976, 1988), on the basis of results of palynological studies, divided the Tomanová Formation into a lower part with a Norian–Rhaetian microflora and an upper sequence with a typical Rhaetian palynoassemblage. Similar palynological observations of the uppermost Triassic strata of the Tatra Mountains were presented by Fijalkowska and Uchman (1993). These researchers identified the palynoassemblage in the “Tomanová beds” as typical for the latest Norian—Rhaetian deposits of the Germanic Basin, and suggested its correlation with the upper part of the Corollina meyeriana Zone of Orłowska-Zwolińska's (1983) palynological scheme for the Polish Keuper. In this paper, the stratigraphic position and age interpretations of these Upper Triassic strata are based on the published analyses of macro- and microflora discussed above, together with lithostratigraphic data.
This section contains the identified ichnotaxa in systematic ichnology, followed by forms that are left in open nomenclature. Material of uncertain designation is also referred to here. Dinosaur tracks from the Tomanová Formation are generally preserved as natural casts. Two ichnites preserved as true tracks (natural moulds) were also found. A total of twenty specimens were found. I identify seven kinds of track morphotypes and briefly summarize here my ichnotaxonomic concepts.
Ornithischia Seeley, 1887
Ichnogenus Anomoepus Hitchcock, 1848
Type species: Anomoepus scambus Hitchcock, 1848, Massachusetts, USA; Portland Formation, Lower Jurassic.
cf. Anomoepus isp.
Fig. 2A, D.
Description.—Two specimens (field observation from Czerwone Zlebki—specimen from Fig. 2A and specimen collected from Czerwone Zlebki and deposited at Tatra Mountains National Park, Zakopane, Poland; Fig. 2D) of tridactyl Anomoepus-like footprints were discovered at Czerwone Zlebki. Both tracks are preserved as natural moulds and are partly eroded and slightly deformed but their morphology (with short digit III which is also separated from the other digits) and size (both are about 15 cm long) are characteristic for the ichnogenus Anomoepus (Olsen and Rainforth 2003). The angle between the digits II and III varies from 25° to 42°, while the angle between the digits III and IV varies from 26° to 57°.
Remarks.—Anomoepus, a purported ornithischian footprint, is a significant component of several diverse ichnofaunas from the Early Jurassic (Olsen and Rainforth 2003). The first unequivocal occurrence of this ichnogenus was reported from the basalmost Hettangian of the Newark Supergroup, eastern USA (Olsen et al. 2002) and from the earliest Jurassic of the Wingate-Kayenta transition zone at Lisbon Valley Oilfield in the western USA (Lockley and Gierliński 2006). Anomoepus tracks were also found in the earliest Hettangian of Poland (Gierliński et al. 2004). Therefore, the two specimens from the Tomanová Formation represent probably the oldest known occurrence of this characteristic ichnogenus.
Ichnogenus Moyenisauropus Ellenberger, 1974
Type species: Moyenisauropus natator Ellenberger, 1974, Lesotho, Africa; Upper Red Beds, Lower Hettangian.
cf. Moyenisauropus isp.
Fig. 2B, c.
Description.—Two specimens (field observations from Czerwone Żlebki) of tridactyl, 20–25 cm long, blunt-toed, and generally robust footprints with Anomoepus-like morphology were found at the Czerwone Żlebki site. Their morphology and size are strongly similar to the Early Jurassic Moyenisauropus ichnogenus (Gierliński 1999; Lockley and Gierliński 2006). Both discovered specimens show imprints of only two phalangeal pads of digit III (see Fig. 2). The angle between the digits II and III varies from 20° to 31°, while the angle between the digits III and IV varies from 29° to 45°.
Remarks.—The ichnogenus Moyenisauropus Ellenberger, 1974 is an intriguing ichnogenus first ilustrated by Ellenberger (1970, 1972, 1974) from the Late Triassic and Early Jurassic ichnofaunas of southern Africa (see also Smith et al. 2009). Ellenberger (1974) named eight ichnospecies of this ichnogenus, which later authors have regarded as a junior synonym of Anomoepus (Olsen and Galton 1984; Haubold 1984; Thulborn 1994; Olsen and Rainforth 2003). New observations suggest that most of the Ellenberger's (1974) material represents typical Anomoepus footprints (Gierliński 1991; Olsen and Rainforth 2003). There are indeed no morphological differences between Anomoepus and most ichnospecies of Moyenisauropus to distinguish them at the ichnogeneric level. However, Moyenisauropus natator (the type ichnospecies of Moyenisauropus) is different from any anomoepodid tracks. Moyenisauropus is distinguished from other tridactyl ornitischian ichnogenera from the Jurassic in having only two phalangeal pads on pedal digit III (Gierliński 1991, 1999; Lockley and Gierliński 2006). In Moyenisauropus the angle between pedal digits II and III, in comparison to that between digits III and IV, is usually larger than in the pes of Anomoepus (Lockley and Gierliński 2006). A new important occurrence of Moyenisauropus tracks was reported from the Early Jurassic of western United States (Lockley and Gierliński 2006) and there is also some diagnostic Moyenisauropus-like tracks from the Late Triassic of Sweden (Milán and Gierliński 2004).
Saurischia Seeley, 1887
Theropoda Marsh, 1881
Ichnogenus Grallator Hitchcock, 1858
Type species: Grallator parallelus Hitchcock, 1858; South Hadley, Massachusetts, USA, Portland Formation, Lower Jurassic.
cf. Grallator isp.
Description.—One specimen of this ichnogenus preserved as natural cast was found (field observation from Czerwone Zlebki). Grallator is the ichnogeneric name applied to relatively small (generally <15 cm long pes) tridactyl tracks of functionally bipedal dinosaurs from the Late Triassic and Early-Middle Jurassic (Olsen et al. 1998; Clark et al. 2004). The pes is narrow, tulip-shaped and digit III projects far anteriorly relative to digits II and IV, which are rather sub-equal in length. The single specimen shows all these characteristics. The angle between the digits II and III is 9°, while the angle between the digits III and IV is 18°.
Remarks.—Grallator tracks are very common in Upper Triassic and Lower Jurassic strata (e.g., Lockley and Hunt 1995; Olsen et al. 1998; Gaston et al. 2003). They are found in the United States, Canada, Europe, Australia and China but are most abundant on the east coast of North America, especially the Upper Triassic and lowermost Jurassic formations of the northern part of the Newark Supergroup (Haubold 1984; Olsen et al. 1998).
Ichnogenus Anchisauripus Lull, 1904
Type species: Anchisauripus sillimani Hitchcock, 1865; Chicopee Falls, Massachusetts, USA, Portland Formation, Lower Jurassic.
Description.—Four specimens of this ichnogenus were found in the Tatra Mountains tracksites (field observations from Czerwone Żlebki and Červený Ŭplaz; specimens from Fig. 3C, E and two specimens collected from Červený Ŭplaz deposited at Slovak National Museum, Bratislava, Slovakia; Fig. 3B and Tatra Mountains National Park, Zakopane, Poland; Fig. 3D). All are partially eroded and deformed, but all specimens possess the characteristic size and morphology for this ichnogenus (Olsen et al. 1998). It is a medium sized functionally tidactyl ichnite (about 17–23 cm long) with relativelly low divarication of outer digits (about 25–30°). All discovered tracks are preserved as natural casts.
Remarks.—As has been discussed by several authors, there are various subtle differences between the type specimens of Grallator parallelus and Anchisauripus sillimani. For example, Olsen (1980) noted that the projection of digit III beyond the two lateral digits (II and IV) decreases rapidly throughout the Grallator—Anchisauripus ichnite assemblages (see Olsen et al. 1998). In addition, the whole footprint size, shape, and the position of the proximal pads are distinguishing features of both ichnotaxa. Although these differences are evident in the type specimens (e.g., Olsen et al. 1998), some authors avoid the use of the ichnogenus Anchisauripus because it is often difficult if not impossible to distinguish this morphotype from large Grallator and small Eubrontes (see Milner and Kirkland 2006).
Ichnogenus Kayentapus Welles, 1971
Type species: Kayentapus hopii Welles, 1971; Moenave Road Tracksite, Arizona, USA, Kayenta Formation, Lower Jurassic.
cf. Kayentapus isp.
Description.—Four specimens (field observations from Červený Ŭplaz and Czerwone Żlebki; specimens from Fig. 4B, D and one specimen collected from Červený Ŭplaz deposited at Slovak National Museum, Bratislava, Slovakia; Fig. 4A and one specimen collected from Czerwone Żlebki and deposited at Tatra Mountains National Park, Zakopane, Poland; Fig. 4C). Those tracks represent a distinguished variant of grallatorid morphology with highly divaricated, elongate digits. The first specimen of that kind (Fig. 4A) was found in Slovakia and described by Michalík et al. (1976) and Michalík and Kundrát (1998). According to the diagnosis based on the method of Weems (1992) and the descriptions presented by Gierliński (1994, 1996), these specimens show characters of the ichnogenus Kayentapus Welles, 1971 (see Gierliński 1996). However, poor preservation of the Polish and Slovakian specimens does not allow ichnospecies-level assignment and precise comparison with known forms of this ichnogenus (see Gierliński 1996). These footprints are also slightly similar to footprints of early ornitchishian dinosaurs such as Anomoepus Hitchcock, 1848 and Moyenisauropus Ellenberger, 1974. However, the projection of digit III beyond the two lateral digits (II and IV) is much greater in Kayentapus than it is in ornithischian tracks (but see specimen of Anomoepus from Fig. 2D). The angle between the digits II and III varies from 34° to 53°, while the angle between the digits III and IV varies from 32° to 57°.
Remarks.—Footprints of Kayentapus are known from deposits of the Norian, Hettangian, Sinemurian, and Pliensbachian of Europe and North America (Weems 1987, 1992; Gierliński 1991, 1996; Gierliński and Ahlberg 1994; Lockley and Hunt 1995; Lockley and Meyer 2000; Gierliński et al. 2004, 2009). According to an osteological restoration presented by Gierliński and Ahlberg (1994), footprints belonging to Kayentapus were made by an Early Jurassic (Hettangian—Sinemurian) early theropod dinosaur similar in pedal anatomy to Dilophosaurus wetherilli Welles, 1970.
Ichnogenus Eubrontes Hitchcock, 1845
Type species: Eubrontes giganteus Hitchcock, 1845; Holyoke, Massachusetts, USA, Portland Formation, Lower Jurassic.
cf. Eubrontes isp.
Description.—A single specimen of a Eubrontes-like footprint was found in Cicha Valley, Červený Ŭplaz, Slovakia (field observation). This specimen is partially eroded but its size (~ 45 cm long) and morphology support referral to Eubrontes. Eubrontes is the ichnogeneric name applied to relatively large (pes length greater than 25 cm) tridactyl tracks of bipedal dinosaurs (Olsen et al. 1998). Digit III is usually relatively shorter than in Grallator and Anchisauripus, but essentially corresponds with grallatorid pattern and looks generally like a robust version of Anchisauripus. The angle between the digits II and III is 18°, while the angle between the digits III and IV is 36°.
Remarks.—A theropod dinosaur is widely-agreed to be the Eubrontes trackmaker (Lockley and Hunt 1995; Olsen et al. 1998; Lockley and Meyer 2000) but some authors have suggested a sauropodomorph affinity for these tracks (e.g., Weems 2003). Since the 1980s, some workers have argued that the earliest occurrence of Eubrontes coincides with the Triassic—Jurassic boundary (see Olsen et al. 1998, 2002). However, other authors suggest that the earliest occurrence of Eubrontes does not coincide with the base of the Jurassic, as there are various well-documented Eubrontes records from the Late Triassic (Gierliński and Ahlberg 1994; Lucas et al. 2006). New occurrences of Late Triassic Eubrontes-like tracks have been reported (Lucas et al. 2006; Dzik et al. 2008), but it is outside the scope of this paper to discuss ichnotaxonomy, morphological variation and stratigraphic positions of those tracks. Preliminary observations, however, suggest that the Late Triassic record of large tridactyl tracks (with pes length greater than 25 cm) may represent rather two or even three different ichnomorphotypes and that the classical ichnospecies Eubrontes giganteus Hitchcock, 1845 is known only from the latest Rhaetian or in Rhaetian—Hettangian transitional beds (Gierliński and Ahlberg 1994; Gierliński et al. 2001, 2004; Dzik et al. 2008).
Sauropodomorpha von Huene, 1932
? Sauropodomorpha indet.
Description.—Two large (about 30–40 cm long), oval-shaped structures similar to earliest Jurassic sauropodomorph dinosaur tracks were found (see Gierliński et al. 2004) in both localities (Czerwone Żlebki, Poland and Červený Ŭplaz, Slovakia; field observations). Similar structures, but organized in a narrow-gauge trackway indicative of a large quadruped animal with strong heteropody (pes larger than manus), have been described from the Late Triassic of Europe, South Africa, and North America (Eosauropus, Lockley et al. 2006).
Remarks.—In all described Late Triassic specimens, the pedal imprints are oval and elongate, tetradactyl to pentadactyl, and possess a long axis and distal claw impressions that are rotated outwards. These features are not clearly visible in the specimens from the Tatra Mountains. The Tatra Mountains specimens are also similar to the Early Jurassic sauropodomorph footrpint Parabrontopodus because both are large in size (Lockley et al. 2006).
Comparison with other Late Triassic ichnofaunas
It is generally accepted that Late Triassic tetrapod footprint assemblages are dominated by archosaurs. The most common are tracks of Brachychirotherium (probable trackmakers are crurotarsans) and tridactyl dinosaur imprints of the Grallator— Anchisauripus—Eubrontes type (Klein and Lucas 2010). There is some controversy among tetrapod ichnologists concerning the presence and validity of other ichnogenera used for Late Triassic tracks, especially Pseudotetrasauropus, Tetrasauropus, Evazoum, Eosauropus, Otozoum (see Klein and Lucas 2010), but also Moyenisauropus (Milán and Gierliński 2004) and Anomoepus (Niedźwiedzki 2005; Gierliński 2009).
Theropod ichnogenera recorded from the Late Triassic of the Tatra Mountains are generally similar to those recorded in successions of the same or similar age in eastern North America (Weems 1987, 1992; Lockley and Hunt 1995), Europe (Haubold 1984; Lockley and Meyer 2000), South Africa (Ellenberger 1972; Olsen and Galton 1984) and South America (Melchor and de Valais 2006). However, some significant differences are apparent. (1) The dinosaur track assemblage from the Tatra Mountains is more diverse. This may be a reflection of either a different degree of study or preservational potential, or perhaps the current age determination of the Tomanová Formation is incorrect and it cannot be considered coeval with these other sites. However, further detailed studies may reveal a possible relationship with Late Triassic tracks described as the ichnogenus Eubrontes. (2) An intriguing single large footprint similar to the Early Jurassic Eubrontes giganteus was identified. Eubrontes tracks are well known from Lower Jurassic strata, especially in southern Africa, Western Europe, eastern North America and the southwestern USA, and some have advocated that the earliest occurrence of Eubrontes corresponds to the Triassic— Jurassic boundary. However, there are well documented Late Triassic records of Eubrontes-like footprints in Australia, southern Africa, Western Europe, Greenland, and North America (Lucas et al. 2006). (3) The presence of possibly ornithischian footprints in the the Upper Triassic Tomanová Formation is remarkable. The morphologically most similar tracks are some of the footprints referred to Anomoepus and Moyenisauropus from Lower Jurassic strata.
The ichnotaxonomic descriptions presented in this paper indicate that many ichnotaxa from the Upper Triassic strata of the Tatra Mountains are comparable to well-known Triassic dinosaur track types (Grallator, Anchisauripus, Kayentapus, and Eubrontes), but also with typical Early Jurassic ichnomorphotypes (Anomoepus, Moyenisauropus). In comparison to other Late Triassic ichnofaunas, this newly recognized ichnoassemblage is the most diverse and includes six, or possibly seven, dinosaur track types (Fig. 7). The most common track types are tridactyl footprints, which are very similar to the Kayentapus, which so far was only recognized in one Late Triassic site of Virginia but is very common in several Early Jurassic tracksites over the world.
Well-preserved Anomoepus-like (Anomoepus—Moyenisauropus group) tracks are widely known from Lower Jurassic strata of Poland (Gierliński 1991, 1999). Anomoepus and Moyenisauropus tracks from the Late Triassic of the Tatra Mountains show considerable morphologic variation in pedal morphology and cannot be accommodated in a single ichnotaxon. The stratigraphic and geographic distribution of Anomoepus—Moyenisauropus tracks offer promise of an improved understanding of early ornithischian evolution, paleoecology and the establishment of palichnostratigraphic zones that may ultimately facilitate correlation of Late Triassic and Early Jurassic vertebrate terrestrial successions.
It is clear from the current study which ichnomorphotypes are present in the Tomanová Formation. However, some tracks require more detailed study, which may require additional material (e.g., cf. Eubrontes isp.). For example, further study of the large and oval-shaped tracks could provide new information about the morphology of the manus and pes of Late Triassic sauropodomorphs, as well as information about the size and ecological behavior of these dinosaurs. Similarly, it remains unclear whether the Late Triassic tracksites of the Tatra Mountains include a truly great taxonomic diversity of tridactyl tracks or preserves many tracks that appear different but actually represent preservational and/or behavioral variations in the tracks of one or two trackmakers.
I am grateful to Andrzej Gaździcki (Institute of Paleobiology, Polish Academy of Sciences, Warsaw, Poland), Jozef Michalik (Geological Institute, Slovakian Academy of Sciences, Bratislava, Slovakia), and Gerard Gierliński (Polish Geological Institute, Warsaw, Poland) for field assistance and helpful comments. I thank Steve Brusatte (American Museum of Natural History, New York, USA) for valuable suggestions and comments. This study was supported by the Polish Ministry of Science and Higher Education, project 3941/B/P01/2009/36. This contribution was presented on the 9th Paleontological Conference (Warszawa, 10–11 October 2008) that was organized by the Institute of Paleobiology of the Polish Academy of Sciences.