Abstract Triassic tetrapod footprints have a Pangaea-wide distribution; they are known from North America, South America, Europe, North Africa, China, Australia, Antarctica and South Africa. They often occur in sequences that lack well-preserved body fossils. Therefore, the question arises, how well can tetrapod footprints be used in age determination and correlation of stratigraphic units? The single largest problem with Triassic footprint biostratigraphy and biochronology is the non-uniform ichnotaxonomy and evaluation of footprints that show extreme variation in shape due to extramorphological (substrate-related) phenomena. Here, we exclude most of the countless ichnospecies of Triassic footprints, and instead we consider ichnogenera and form groups that show distinctive, anatomically-controlled features. Several characteristic footprint assemblages and ichnotaxa have a restricted stratigraphic range and obviously occur in distinct time intervals. This can be repeatedly observed in the global record. Some reflect distinct stages in the evolutionary development of the locomotor apparatus as indicated by their digit proportions and the trackway patterns. Essential elements are archosaur tracks with Rotodactylus , the chirotherian ichnotaxa Protochirotherium , Synaptichnium , Isochirotherium , Chirotherium and Brachychirotherium , and grallatorids that can be partly linked in a functional-evolutionary sequence. Non-archosaur footprints are common, especially the ichnotaxa Rhynchosauroides , Procolophonichnium , Capitosauroides and several dicynodont-related or mammal-like forms. They are dominant in some footprint assemblages. From the temporal distribution pattern we recognize five distinct tetrapod-footprint-based biochrons likened to the known land-vertebrate faunachrons (LVFs) of the tetrapod body fossil record: 1. Dicynodont tracks (Lootsbergian=Induan age); 2. Protochirotherium ( Synaptichnium ), Rhynchosauroides , Procolophonichnium (Nonesian=Induan–Olenekian age); 3. Chirotherium barthii , C. sickleri , Isochirotherium , Synaptichnium (‘ Brachychirotherium ’), Rotodactylus , Rhynchosauroides , Procolophonichnium , dicynodont tracks, Capitosauroides (Nonesian–Perovkan=Olenekian–early Anisian); 4. Atreipus–Grallator (‘ Coelurosaurichnus ’), Synaptichnium (‘ Brachychirotherium ’), Isochirotherium , Sphingopus , Parachirotherium , Rhynchosauroides , Procolophonichnium (Perovkan–Berdyankian=Late Anisian–Ladinian); 5. Brachychirotherium , Atreipus – Grallator , Grallator , Eubrontes , Apatopus , Rhynchosauroides , dicynodont tracks (Otischalkian–Apachean=Carnian–Rhaetian). Tetrapod footprints are useful for biostratigraphy and biochronology of the Triassic. However, compared to the tetrapod body fossil record with eight biochrons, the five footprint-based biochrons show less resolution of faunal turnover as ichnogenera and ichnospecies at best reflect biological families or higher biotaxonomic units. Nevertheless, in sequences where body fossils are rare, footprints can coarsely indicate their stratigraphic age.

Abstract The footprints called ‘ Chirotherium ’, because of their resemblance to human hands, were found in Triassic sandstones from Germany in 1834 and Cheshire in 1838. As no bones or other fossil remains were found at either locality, the trackmaker's identity was a mystery. Marsupial mammals were first suggested but in 1842 Richard Owen confidently identified the prints as those of labyrinthodont amphibians. Later discoveries in Cheshire and elsewhere indicated that the trackmakers were more likely to have been pseudosuchian reptiles. In 1965 strong confirmation of this view came from the discovery in Switzerland of the skeleton of Ticinosuchus ferox. The absence of fossil remains associated with the footprints has always been ascribed to the arid climate of Triassic times – a view reinforced by Henry Charles Beasley in 1907 . A more moderate viewpoint was put forward by George Highfield Morton in 1898, who took note of the traces of flora found in the local Triassic strata. Pictorial representations of the Anisian through the late nineteenth and twentieth centuries indicate varying interpretations of the degree of aridity from sparsely vegetated landscapes to sand sea desert. Recent work shows that the environment in a local context was more richly vegetated and humid than had previously been supposed and that the historical interpretation of aridity has probably been overstated. A modern context may, perhaps, be seen in the river valleys of the Atacama Desert in northern Chile. Here, permanent fertile fluvial systems support a mixed indigenous flora of giant horsetails and conifers. The flora displays an adaptation to high groundwater salinity, which may have lessons in interpretation of the Anisian environment.

Abstract We present the first comprehensive description of Prorotodactylus and Rotodactylus dinosauromorph tracks from the Early and Middle Triassic of the Holy Cross Mountains, Poland. We describe and comprehensively figure tracks that have been mentioned briefly in previous accounts as well as new, recently discovered material, and analyse the variation and stratigraphic distribution of these specimens. Tracks have been recorded from four sites – Koszary, Stryczowice, Wióry and Baranów – which span the early Olenekian–early Anisian ( c. 250–246 Ma). These tracks therefore represent an ichnological record of the evolutionary succession of early dinosauromorphs during the earliest part of their evolutionary history. Recognized track types include cf. Prorotodactylus isp . , Prorotodactylus isp., Prorotodactylus mirus , Rotodactylus cursorius , Rotodactylus isp. and cf. Rotodactylus isp. At least three distinct Early and early Middle Triassic early dinosauromorph ichnofaunas can be recognized. The oldest, which is early Olenekian in age, is characterized by the presence of Prorotodactylus isp., cf. Prorotodactylus isp . and non-archosaurian archosauromorph or archosaur tracks (e.g. Synaptichnium isp., Protochirotherium isp.), recorded at the Stryczowice and Koszary sites. The following assemblage, recorded at the late Olenekian Wióry site, displays the highest ichnodiversity of dinosauromorphs, with four track types present ( Prorotodactylus isp., Prorotodactylus mirus , Rotodactylus cursorius and cf. Rotodactylus isp.). The youngest site, Baranów, includes Rotodactylus isp., as well as other larger dinosauromorph tracks. The first body fossil evidence of dinosauromorphs is a few million years younger than the youngest Polish tracks, so Prorotodactylus and Rotodactylus tracks currently provide the oldest record of dinosauromorph morphology, biology and evolution.

Abstract German geologists began to study rocks now recognized as Triassic during the late 1700s. In 1823, one of those German geologists, a very astute mining engineer named Friedrich August von Alberti (1795–1878), coined the term ‘Trias formation’ for an c . 1 km thick, tripartite succession of strata in southwestern Germany – the Bunten Sandsteins, Muschelkalk and Keuper of the German miners. Alberti also recognized Triassic rocks outside of Germany, throughout much of Europe and as far away as India and the United States. By the end of the nineteenth century, Triassic rocks had been identified across Europe and Asia, and in North America, South America and Africa. Indeed, in 1895, the Austrian geologist Edmund von Mojsisovics (1839–1907) and his collaborators published a complete subdivision of Triassic time based on ammonoid biostratigraphy and, in so doing, introduced many of the Triassic chronostratigraphic terms still used today. The twentieth century saw the elaboration of an ammonoid-based Triassic timescale, especially due to the work of Canadian palaeontologist E. Timothy Tozer (1928-). During the last few decades, work also began on developing a global magnetic polarity timescale for the Triassic, a variety of precise numerical ages tied to reliable Triassic biostratigraphy have been determined, and conodont biostratigraphy has become an important tool in Triassic chronostratigraphic definition and correlations. The current Triassic chronostratigraphic scale is a hierarchy of three series (Lower, Middle, Upper) divided into seven stages (Lower = Induan, Olenekian; Middle=Anisian, Ladinian; and Upper=Carnian, Norian, Rhaetian) further divided into 15 substages (Induan=upper Griesbachian, Dienerian; Olenekian=Smithian, Spathian; Anisian=Aegean, Bithynian, Pelsonian, Illyrian; Ladinian=Fassanian, Longobardian; Carnian=Julian, Tuvalian; Norian=Lacian, Alaunian, Sevatian). Ammonoid and conodont biostratigraphies provide the primary basis for the chronostratigraphy. A sparse but growing database of precise radioisotopic ages support these calibrations: base of Triassic c . 252 Ma, base Olenekian c . 251 Ma, base Anisian c . 247 Ma, base Ladinian c . 242 Ma, base Jurassic c . 201 Ma. A U/Pb age of c . 231 Ma from the Italian Pignola 2 section is lower Tuvalian, and U/Pb ages on detrital zircons from the nonmarine Chinle Group of the western USA of c . 219 Ma are in strata of late Carnian (Tuvalian) age based on the biostratigraphy of palynomorphs, conchostracans and tetrapods. These data support placement of the Norian base at c . 217 Ma, and indicate that the Tuvalian is more than 10 million years long and that the Carnian and Norian are the longest Triassic stages. Magnetostratigraphic data establish normal polarity for all of the Triassic stage bases except Anisian and Ladinian. An integrated biostratigraphic correlation web for the marine Triassic consists of ammonoids, bivalves, radiolarians and conodonts, whereas a similar web exists for the nonmarine Triassic using palynomorphs, conchostracans and tetrapods. Critical to cross correlation of the two webs is the Triassic section in the Germanic basin, where a confident correlation of nonmarine biostratigraphy to Triassic stage boundaries has been achieved. The major paths forward in development of the Triassic timescale are: finish formal definition of all Triassic stage boundaries, formally define the 15 Triassic substages, improve the integration of the Triassic biostratigraphic webs and develop new radioisotopic and magnetostratigraphic data, particularly for the Late Triassic.

Abstract The Triassic timescale based on nonmarine tetrapod biostratigraphy and biochronology divides Triassic time into eight land-vertebrate faunachrons (LVFs) with boundaries defined by the first appearance datums (FADs) of tetrapod genera or, in two cases, the FADs of a tetrapod species. Definition and characterization of these LVFs is updated here as follows: the beginning of the Lootsbergian LVF=FAD of Lystrosaurus ; the beginning of the Nonesian=FAD Cynognathus ; the beginning of the Perovkan LVF=FAD Eocyclotosaurus ; the beginning of the Berdyankian LVF=FAD Mastodonsaurus giganteus ; the beginning of the Otischalkian LVF=FAD Parasuchus ; the beginning of the Adamanian LVF=FAD Rutiodon ; the beginning of the Revueltian LVF=FAD Typothorax coccinarum ; and the beginning of the Apachean LVF=FAD Redondasaurus . The end of the Apachean (= beginning of the Wasonian LVF, near the beginning of the Jurassic) is the FAD of the crocodylomorph Protosuchus . The Early Triassic tetrapod LVFs, Lootsbergian and Nonesian, have characteristic tetrapod assemblages in the Karoo basin of South Africa, the Lystrosaurus assemblage zone and the lower two-thirds of the Cynognathus assemblage zone, respectively. The Middle Triassic LVFs, Perovkan and Berdyankian, have characteristic assemblages from the Russian Ural foreland basin, the tetrapod assemblages of the Donguz and the Bukobay svitas, respectively. The Late Triassic LVFs, Otischalkian, Adamanian, Revueltian and Apachean, have characteristic assemblages in the Chinle basin of the western USA, the tetrapod assemblages of the Colorado City Formation of Texas, Blue Mesa Member of the Petrified Forest Formation in Arizona, and Bull Canyon and Redonda formations in New Mexico. Since the Triassic LVFs were introduced, several subdivisions have been proposed: Lootsbergian can be divided into three sub-LVFs, Nonesian into two, Adamanian into two and Revueltian into three. However, successful inter-regional correlation of most of these sub-LVFs remains to be demonstrated. Occasional records of nonmarine Triassic tetrapods in marine strata, palynostratigraphy, conchostracan biostratigraphy, magnetostratigraphy and radioisotopic ages provide some basis for correlation of the LVFs to the standard global chronostratigraphic scale. These data indicate that Lootsbergian=uppermost Changshingian, Induan and possibly earliest Olenekian; Nonesian=much of the Olenekian; Perovkan=most of the Anisian; Berdyankian=latest Anisian? and Ladinian; Otischalkian=early to late Carnian; Adamanian=most of the late Carnian; Revueltian=early–middle Norian; and Apachean=late Norian–Rhaetian. The Triassic timescale based on tetrapod biostratigraphy and biochronology remains a robust tool for the correlation of nonmarine Triassic tetrapod assemblages independent of the marine timescale.