Stephan Spiekman

• PhD
• PostDoc Position at State Museum of Natural History Stuttgart

Tanystropheus longobardicus is one of the most remarkable and iconic Triassic reptiles. Mainly known from the Middle Triassic conservation Lagerstätte of Monte San Giorgio on the Swiss-Italian border, it is characterized by an extraordinarily long and stiffened neck that is almost three times the length of the trunk, despite being composed of only...

The historical clade “Protorosauria” represents an important group of archosauromorph reptiles that had a wide geographic distribution between the Late Permian and Late Triassic. “Protorosaurs” are characterized by their long necks, which are epitomized in the genus Tanystropheus and in Dinocephalosaurus orientalis . Recent phylogenetic analyses ha...

We describe a new small-bodied coelophysoid theropod dinosaur, Pendraig milnerae gen. et sp. nov, from the Late Triassic fissure fill deposits of Pant-y-ffynnon in southern Wales. The species is represented by the holotype, consisting of an articulated pelvic girdle, sacrum and posterior dorsal vertebrae, and an associated left femur, and by two re...

Non‐crocodyliform crocodylomorphs, formerly referred to the informal group ‘Sphenosuchia’, are the earliest known crocodylomorph precursors of extant crocodylians. They are therefore crucial for our understanding of early crocodylian evolution and the origin of typical crocodylian characteristics, such as the formation of a secondary palate, comple...

The non-archosauriform archosauromorph Dinocephalosaurus orientalis was first described from the Upper Member of the Guanling Formation (late Anisian, Middle Triassic) of Guizhou Province by Li in 2003 on the basis of a complete articulated skull and the first three cervical vertebrae exposed in dorsal to right lateral view. Since then, additional...

Since the early nineteenth century, the Central European Basin (CEB) has been a historically important region for the study of terrestrial tetrapods from the Triassic Period, and continues to yield a wealth of new finds. A review of the fossil evidence permits the recognition of new patterns of diversity for various clades during the recovery perio...

The Triassic was a key period in the evolution of vertebrates, and reptiles in particular, giving rise to a plethora of successful lineages, some of which are still extant. One of the groups that flourished during the early Mesozoic were the tanysaurians (Archosauromorpha: Tanysauria). They had elongate neck vertebrae that in some genera reached ex...

The Triassic period saw the emergence and diversification of a plethora of successful lineages of reptiles, some of which are still extant (e.g. turtles, squamates, rhynchocephalians, crocodylians). Among the evolutionarily successful groups of the early Mesozoic, tanysaurians (Tanysauria, Archosauromorpha) exhibited especially disparate lifestyles...

The earliest crocodylomorphs, known as non‐crocodyliform crocodylomorphs, first appeared during the Late Triassic. In contrast to extant crocodylians, which are all semi‐aquatic, early crocodylomorphs represent terrestrial taxa with a fully erect posture and in most cases a small body size. Their gracile skeletons suggest an active mode of life, po...

The Triassic radiation of vertebrates saw the emergence of the modern vertebrate groups, as well as numerous extinct animals exhibiting conspicuous, unique anatomical characteristics. Among these, members of Tanystropheidae (Reptilia: Archosauromorpha) displayed cervical vertebral elongation to an extent unparalleled in any other vertebrate. Tanyst...

Some of the earliest members of the archosaur-lineage (i.e., non-archosauriform archosauromorphs) are characterised by an extremely elongated neck. Recent fossil discoveries from the Guanling Formation (Middle Triassic) of southern China have revealed a dramatic increase in the known ecomorphological diversity of these extremely long-necked archosa...

Marine conservation deposits (‘Konservat-Lagerstätten’) are characterized by their mode of fossil preservation, faunal composition and sedimentary facies. Here, we review these characteristics with respect to the famous conservation deposit of the Besano Formation (formerly Grenzbitumenzone; including the Anisian–Ladinian boundary), and the success...

During the Mesozoic several clades of reptiles diversified into a wide range of marine niches. One of the most striking and evolutionary successful strategies among these adaptations included extreme neck elongation combined with the presence of a relatively small head. This bauplan evolved independently in the archosauromorphs Tanystropheus and Di...

Crocodylomorpha is the stem-lineage of modern crocodylians and the only pseudosuchian (i.e. crocodylian-line archosaurs) clade that survived the Triassic–Jurassic mass extinction event. Its earliest members, the non-crocodyliform crocodylomorphs, also known as ‘sphenosuchians’, were terrestrial and mostly small-bodied (<2 m long), although some lar...

Extreme neck elongation was a common evolutionary strategy among Mesozoic marine reptiles, occurring independently in several lineages1,2. Despite its evolutionary success, such an elongate neck might have been particularly susceptible to predation1, but direct evidence for this possibility has been lacking. Composed of only 13 hyperelongate verteb...

A long neck is an evolutionary innovation convergently appearing in multiple tetrapod lineages, including groups of plesiosaurs, non-archosauriform archosauromorphs, turtles, sauropodomorphs, birds, and mammals. Among all tetrapods both extant and extinct, two Triassic archosauromorphs, Tanystropheus and Dinocephalosaurus, have necks that are parti...

In the aftermath of the Permo-Triassic mass extinction event, several reptile lineages radiated to form major components of marine faunas during the entire Mesozoic. The Lower Muschelkalk, which was deposited within a shallow inland sea in the Germanic Basin during the Middle Triassic, is one of the most important regions for understanding the earl...

The frameshift hypothesis is a widely accepted model of bird wing evolution. This hypothesis postulates a shift in positional values, or molecular-developmental identity, that caused a change in digit phenotype. The hypothesis synthesized developmental and paleontological data on wing digit homology. The “most anterior digit” (MAD) hypothesis prese...

The postcranial morphology of the extremely long-necked Tanystropheus hydroides is well-known, but observations of skull morphology were previously limited due to compression of the known specimens. Here we provide a detailed description of the skull of PIMUZ T 2790, including a partial endocast and endosseous labyrinth, based on synchrotron microt...

The genus Macrocnemus is a member of the Tanystropheidae, a clade of non-archosauriform archosauromorphs well known for their very characteristic, elongated cervical vertebrae. Articulated specimens are known from the Middle Triassic of Alpine Europe and China. Although multiple articulated specimens are known, description of the cranial morphology...

Over the past decades, an increasing number of reptiles have been described from the Middle Triassic of southern parts of China. Marine reptiles such as thalattosaurs, ichthyosaurs and sauropterygians dominated these paleofaunas and are known to have had a Tethys-wide distribution. Indeed, several species have been described from both the eastern a...

Over the past decades, an increasing number of reptiles have been described from the Middle Triassic of southern parts of China. Marine reptiles such as thalattosaurs, ichthyosaurs and sauropterygians dominated these paleofaunas and are known to have had a Tethys‐wide distribution. Indeed, several species have been described from both the eastern a...

Correctly identifying taxa at the root of major clades or the oldest clade-representatives is critical for meaningful interpretations of evolution. A small, partially crushed skull from the Late Triassic (Norian) of Connecticut, USA, originally described as an indeterminate rhynchocephalian saurian, was recently named Colobops noviportensis and rei...

Tanystropheus represents one of the most characteristic genera of Triassic reptiles and is typified by easily recognizable, hyperelongate cervical vertebrae. First described in 1852, isolated cervical vertebrae and other remains have been referred to the genus and various species have been erected and rejected based on this material. This has resul...

Tanystropheids were archosauromorph reptiles from the Triassic characterized by long necks composed of elongate cervical vertebrae and ribs, as is epitomized by its most recognisable genus Tanystropheus. An isolated cervical vertebra from the Winterswijk quarry was assigned to Tanystropheus antiquus in 1984. However, the genus Tanystropheus has bee...

Tanystropheids were archosauromorph reptiles from the Triassic characterized by long necks composed of elongate cervical vertebrae and ribs, as is epitomized by its most recognisable genus Tanystropheus. An isolated cervical vertebra from the Winterswijk quarry was assigned to Tanystropheus antiquus in 1984. However, the genus Tanystropheus has bee...

Abstract Prolacerta broomi is an Early Triassic archosauromorph of particular importance to the early evolution of archosaurs. It is well known from many specimens from South Africa and a few relatively small specimens from Antarctica. Here, a new articulated specimen from the Fremouw Formation of Antarctica is described in detail. It represents th...

The aim of the present chapter is to provide a general overview of the main developmental differences among the three major mammalian groups, to characterize mammals among amniotes, and to present some crucial aspects of the anatomy and physiology of mammalian embryogenesis. We cover different aspects of embryology in a chronological order. We firs...

Development in marsupials is specialized towards an extremely short gestation and highly altricial newborns. As a result, marsupial neonates display morphological adaptations at birth related to functional constraints. However, little is known about the variability of marsupial skull development and its relation to morphological diversity. We studi...

The recent transfer of the palaeontological collections of the former Geologisch Museum of Delft University to Naturalis Biodiversity Center (Leiden) has led to the rediscovery of the skull and mandible of the ceratopsian dinosaur Protoceratops. The specimen originates from Campanian aeolian sandstone deposits of the Flaming Cliffs in Mongolia, hav...

The recent transfer of the palaeontological collections of the former Geologisch Museum of Delft University to Naturalis Biodiversity Center (Leiden) has led to the rediscovery of the skull and mandible of the ceratopsian dinosaur Protoceratops. The specimen originates from Campanian aeolian sandstone deposits of the Flaming Cliffs in Mongolia, hav...