Fossil flora and fauna in the Posidonia Shale, Germany
18x6 m fossilized floating wood (Agathoxylon), with Crinoids attached (Pentacrinites & Seirocrinus). It is one of the most emblematic fossils of the formation, where the anoxic seas of the lower toarcian lead to an exquisite preservation.
The Sachrang Formation or "Posidonienschiefer" Formation (common name the "Posidonia Shale") is a geological formation of southwestern Germany, northern Switzerland, northwestern Austria, southeast Luxembourg and the Netherlands, that spans about 3 million years during the Early Jurassic period (early Toarcian stage). It is known for its detailed fossils, especially marine biota, listed below.[1] Composed mostly of black shale, the formation is a Lagerstätte, where fossils show exceptional preservation (including exquisite soft tissues), with a thickness that varies from about 1 m to about 40 m on the Rhine level, being on the main quarry at Holzmaden between 5 and 14 m.[1] Some of the preserved material has been transformed into the fossil hydrocarbon jet which, especially jet derived from wood remains, is used for jewelry.[2] The exceptional preservation seen in the Posidonia Shale has been studied since the late 1800s, finding that a cocktail of chemical and environmental factors led to such an impressive preservation of the marine fauna.[2] The most common theory is that changes in the oxygen level, where the different anoxic events of the Toarcian left oxygen-depleted bottom waters, stopped scavengers from consuming the dead bodies.[3]
The "Monotis"-Dactylioceras bed shows an accumulation of the bivalves Meleagrinella substriata and the ammoniteDactylioceras, that were the most abundant representatives of its group on the Altdorf region, and were probably washed to near epicontinental waters by a rapid event, or as result of a large succession of events.[4] This assemblage has been compared with modern Brazilian coastal mangroves and also linked to tsunami events.[5]
Hybodus hauffianus with skin and Belemnnite traces
Several empty ammonite shells from Holzmaden have been found with associated decapods inside.[6] This includes a possible member of the genus Paleastacus inside a chamber of a Harpoceras.[6] This decapod is related to the family Erymidae, which are considered to be possible bottom-dweller carnivores or carrion feeders.[6] The associated fossil has several spherical structures that had been interpreted as decapod coprolites, implying that the animal lived for a long period within the shell.[6] More recent studies had recovered new data about the inquilinism of decapods inside ammonites, this time, however, recovering three eryonoids together within a body chamber.[7] The eryonoids most likely used the ammonoid as some kind of shelter, possibly due to the shell being an ideal location to molt, protection against predators, a source of food or that the shell was used as a long-term shelter.[7] One key aspect found was that the muddy bottom was not suitable for burrowing, implying that the decapods inhabited a different shelter due to being unable to make their own.[7] Other biota are found related to the decayed ammonite shells, such as serpulid annelids and bivalves, creating what was denominated as "benthic islands".[6]
Beyond trace fossils, several vertebrate specimens show associations with crustacean exoskeletal remains such as GPIT-PV-31586 and SMNS 58389 (Pachycormus macropterus) with necrophagous interaction as well SMNS 55934 (Stenopterygius quadriscissus) or SMNS 95401 (Metopacanthus sp.).[8]
The genus Clarkeiteuthis and its predatory behaviour, found associated with fishes of the genus Leptolepis.[9] Based on the position of prey and predator, it was suggested that the cephalopods caught and killed the fishes while the schools were still in well-oxygenated waters and then descended into oxygen-depleted water layers where the cephalopod suffocated and died attached to its prey.[9] The cephalopods’ arms were contracted over the fish, likely killing it quickly by cutting its spine.[9]
Several Geotheutis have been reported with eumelanin preserved along with their ink sacs.[10]
A specimen of Jeletzkyteuthis found in Ohmden has appeared predating a Parabelopeltis. The association of these 2 genera shows the predatory behaviour of this group when its members lived in epicontinental seas, which is rather different than extant Vampyromorphs.[11]
A pabulite (fossilized meal which never entered the digestive tract) was recovered from Holzmaden, being composed of an associated Passaloteuthis laevigata with its arms embracing an exuvia of a crustacean.[12] The belemnnite itself can be seen as the remnant of a failed predation attempt from a Hybodus, corroborating a possible tropic chain.[12]
Stenopterygius quadriscissus, mother with embryo
One of the most complex organism interactions on the Posidonia Shale were the crinoid megarafts that grouped a wide variety of animals, creating large floating ecosystems.[13] The largest megaraft found measured 18 metres (59ft), and is based on an Agathoxylon trunk, where different animals were attached.[13] The first attached animals would have been the growing community of oysters, bivalves and crinoids, that would add a small weight to the raft (about 800 kilograms (1,800lb)).[13] The presence of these megarafts were in part possible due to the absence of marine wood worms which destroy tree logs in less than 3 years along with the absence of modern raft wood predators (that appeared on the Bathonian). These rafts could last up to 5 years, which is the main reason the crinoids attached were able to reach huge sizes.[13] These rafts were likely also essential to distribute animals along sea basins.[13]Seirocrinus & Pentacrinites were some of the main crinoid colonizers of the floating rafts.[14]Seirocrinus is the main representative of the pelagic crinoids, being among the longest animals known, reaching 26 m long in the largest documented specimen.[14] The ecology of the genus is widely known, with it being known that the smallest stems were among the first animals to colonize the rafts, with at least 2 generations of crinoids found per raft, where the hydrodynamic changes of the log influenced the settlement of the crinoids.[14] It is believed that Seirocrinus underwent seasonal reproduction linked to monsoonal conditions that sent new logs to the sea.[14] The large crinoids would have feed on pelagic micronutrients, and after the log fell to the bottom, all of the colony would have died.[14]
Thoracic barnacles of the genus Toarcolepas became the oldest epiplanktonic barnacle known in the fossil record, probably motivated by the appearance of the giant crinoid rafts. It has been found in situ associated with fossil wood.[15]
Fossil of Clarkeiteuthis preying on Leptolepis
The shark Hybodus includes specimens with gastric contents full of belemnnite fragments.[16] This implies active predatory behaviour by the genus towards several kinds of belemnnites, such as Youngibelus.[16]
A speiballen (a regurgitated mass composed of indigestible stomach contents) had been found in the Holzmaden quarry.[17] The speiballen measures 285mm in length with a diameter of 160mm, and consists of 4 members of the genus Dapedium (Dapediidae) and a jaw identified as Lepidotes (Semionotidae).[17] The maker of this speiballen has been suggested to be a shark like Hybodus, an actinopterygian or a marine reptile.[17]
A specimen of Pachycormus has been found with stomach contents that include hooks similar to the ones found on genera like Clarkeiteuthis.[18]
Another specimen of Pachycormus macropterus preserves an ammonite inside its gut, likely swallowed by accident and directly responsible for the fish's death.[19]
SMNS 51144 (Saurostomus esocinus) was found with Chondrites sp. burrows in the abdominal cavity, what indicates a possible opportunistic scavenger. Other Chondrites sp. includes SMNS 17500 and MHH 1981/25 (Stenopterygius uniter) that either suggest the ichthyosaurs were preserved immediately below one such bioturbation horizon or scavenger association.[8]
The known specimens of Toarcocephalus are evidence of successful predation events, as the head of one was isolated, likely as product of a decapitation, with another preserved within a regurgitated mass.[20]
One of the most emblematic finds of the formation is that of a mother Stenopterygius giving birth to live young. While specimens have been found with embryos, the bones of these embryos are scattered partly beyond the body limits of the mother.[21] There have been various theories about this scenario: either the bones of embryos had been deposited before the body of the adult went to the sea floor, or in the ichthyosaurs’ last moments where it sank to the bottom and may have given untimely birth to some of the foetuses, and finally another option follows post mortem hydrostatic pressure being too high to be prevented by the body, exploding or expelling its embryos.[22]
The specimen SMNS 53363 (Eurhinosaurus?) from Aichelberg was found with two encrusted large oysters (Liostrea) on the right pterygoid, considered to be part of a reef stage over bones.[8]
SMNS 80234 (Stenopterygius quadriscissus) represents another female with embryos, yet also shows ribs broken perimortem that may represent either intraspecific aggression or a predation attempt. This specimen has several taxa associated: ammonite aptychi, two ophiuroids (Sinosura brodiei) and an articulated echinoid (Diademopsis crinifera) indicate a short-lived deadfall community.[8]
SMNS 81841 (Stenopterygius quadriscissus) represents one of the clearest examples of deadfall communities described in the formation: the skeleton is associated with serpulids surrounded by a mass of disarticulated ophiuroid remains, indeterminate echinoid tests, an isolated crinoid ossicle, the byssate bivalve Oxytoma inaequivalvis, the pectinid Propeamussium pumilus, Eopecten strionatis, Plagiostoma sp., Meleagrinella sp., "Cucullaea" muensteri, with the genera Parainoceramya dubia and Liostrea associated with the carcass.[23] As many of these bivalves show overgrowth the community likely persisted for some time.[23] Fossil traces of Gastrochaenolites isp. attributed to mechanical bivalve borers are abundant implicating prolonged exposure of the skeleton on the seafloor.[23]
SMNS 81719 (Stenopterygius uniter) includes Liostrea, Propeamussium pumilus, Plagiostoma sp. and Parainoceramya dubia, with other invertebrates found (?) not being part of the deadfall community, such as several ammonites and Parainoceramya valves, being stratigraphically below the specimen.[8] This specimen includes also traces of scavenging activity, possibly by crustaceans.[8]
SMNS 80113, (Stenopterygius triscissus) was found populated by Parainoceramya, a specimen of Eopecten strionatis and an unexpected specimen of the small infaunal lucinid Mesomiltha pumila, equivocal evidence for the sulfophilic stage.[8]
Local ichthyosaur soft tissues include skin enough well preserved to infer coloration and appearance on the living animal, as well evidence for homeothermy and crypsis.[24]
Gut contents of the local pterosaurs are known: Campylognathoides preserves hooks of the coleoid Clarkeiteuthis (therefore being one of the few teuthophagous pterosaurs), while Dorygnathus preserves remains of Leptolepis.[25]
Microbial activity
Non-fenestrate stromatolite crusts formed in aphotic deep-water environments during intervals of very low sedimentation are recovered in places such as Teufelsgraben, Hetzles.[26] The stromatolites of this region have evidence of live on a deeper shelf environment with a quietwater deposit which suffered repeated phases of stagnant bottom waters, where a depth water habitat developed, probably at more than 100 meters depth.[26] There is a thin, southern widespread stromatolite crust on the top of the Sachrang Formation, called "Wittelshofener Bank", that has made researchers rethink the depth of the major southern basin of the formation, where the absence of phototrophic calcareous benthic organisms (probably due to the lack of light) shows the depth of the basin.[26] On the "Wittelshofener Bank" there is also the only occurrence of ooids, presumably formed in the same deep-water environment.[26]
Probably related with archaeal activity.[26] Although Frutexites is a cryptic microfossil and an important element of many deep water stromatolites, with an inorganic origin proposed it was interpreted as dendritic shrubs of purely inorganic growth of aragonitic crystals, but it also resembles shrubs of the cyanobacteria Angulocellularia.[26] In the Posidonia Shale a cryptoendopelitic mode of life is assumed, being only possible for heterotrophic bacteria or fungi.[26] As seen in the stromatolites of the Posidonia Shale, Frutexites acted mainly as a dweller or secondary binder of the deep-water stromatolites, not as their major constructor.[26]
A cyanobacteria, member of the family Oscillatoriales. Girvanella is almost rock-forming in the lower and upper levels, and is very common, but can only rarely be detected in the bituminous clay marl slate due to preservation reasons.[27]
A dinoflagellate cyst, type member of Luehndeoideae. Luehndea spinosa is common in the middle layers of the lower Sachrang Formation, while restricted to certain areas in younger ones.[34]
A dinoflagellate cyst, member of Dinophyceae of the family Nannoceratopsiaceae. In the Lias Epsilon Interval (Lowermost Toarcian), most of the assemblages are dominated by Nannoceratopsis gracilis. Nannoceratopsis senex becomes highly abundant until the uppermost Tenuicostatum.[34]
The Posidonia Shale preserves an abundant variety of algae, such as the genus of colonial green algae Botryococcus, or the unicellular algal bodies Tasmanites, and other small examples. Algae are a good reference for changes on the oxygen conditions along the Toarcian.[37]
An acritarch probably of algal origin. It is abundant in most of the samples studied from the Sachrang Formation, being nearly the 50% of the acritarch fraction on some locations.
A member of the family Parhabdolithaceae inside Stephanolithiales. The abundance drop of M. jansae further characterises the T-OAE perturbation, where it becomes the dominant genus in most of the Saxony Basin.
Type member of the family Schizosphaerellaceae inside Parhabdolithaceae. Towards the Pliensbachian-Toarcian extincion this genus decreases in abundance and size.
A member of the Prasinophyceae. Often found in basinal deposits
Fungi
Fungal spores, hyphae and indeterminate remains are a rare element of the otherwise open marine deposits of the Posidonienschiefer formation, but were recovered at Dormettingen.[46] These fungal remains are composed mostly of indeterminate spores and indicate oxygenated environments and suitable transportation by rivers.[46]
Fungal patches in ammonite shells and belemnite rostra
A marine parasitoid fungus of uncertain relationship, linked with shells of marine invertebrates. The extant Ostracoblabe implexa is usually found associated with bivalve shells as an external parasitoid. Beyond this genus, other fungal remains include indeterminate endolithic fungi linked with microbial mats.
Ichnofossils
The major ichnological analyses of the Posidonian Shale come from Dotternhausen/Dormettingen, where the ichnogenus Phymatoderma formed the so-called Tafelfleins and Seegrasschiefer.[48] The Tafelflein bed was deposited under anoxic bottom and pore water, where a recover of oxygen allow the Phymatoderma-producers return.[48] The two organic-rich layers (Tafelfleins and Seegrasschiefer) are characterized by the dense occurrence of trace fossils such as Chondrites and Phymatoderma, done episodically due to the fall of the oxygen levels.[48] The coeval more nearshore Swiss deposits referred Posidonian Shale (Rietheim Member) hosted similar trace fossils to those recovered on SW Germany.[48] Ichnofossils in this setting apparently evolved faster to more oxic-to-dysoxic bottom waters.[48] At Unken, laminated deposits of red limestone suggest well oxygenated active waters (as they lack shale), where high amounts of Chondrites are found.[40]
In the non-bituminous facies located on Obereggenen im Breisgau (Shore of the Black Forest High), especially the lower semicelatum subzone, pyritized individual needles of silica sponges (Demospongiae and Hexactinellida) are found, rarely on pelagic layers to very often on the low depth marine deposits.[27] They are usually associated with radiolarian stone cores. In Dusslingen and Reutlingen, these sponge needles are sometimes barytized in phosphorites of the Haskerense subzone and are much more common here than in any other zone of the Lower Toarcian. These needles are absent in the bituminous horizons of the entire Lower Toarcian.[27] Increased amounts of sponge needles (dominated by Hexactinellida) are also found on the arenaceous facies of the nearshore unit that is the Unken member, being the only section if its region hosts them, probably due to be an active and well oxygenated bottom.[40] The location of this member as a possible bay on the south of the vindelician land probably allow to the development of more pre-Toarcian AOE conditions, hence the presence of biota otherwise rare on bituminous layers.[40]
A Lingulidaerhynchonellatan. Associations of bioturbating infauna are dominated in certain sections by Palaeonucula/Lingula aggregations, developed under longer-term oxygenated conditions within the substrate and bottom waters.[57]
A Discinidaerhynchonellatan. This genus was found to have a planktotrophic larval stage that adapted while growing to the local redox boundary. When this fluctuated near the sediment–water interface and oxygen availability prevailed, it allowed benthic colonization. It is found in associations with Grammatodon and Pseudomytiloides.[57]
A posidoniidostreoidan. It is the type fossil of the Sachrang Formation. Originally it was named "Posidonia bronni", thought to be a new genus, and the strata were denominated the Posidonia layers after it. Years later it turned out to be a junior synonym of Bositra, and thus it was reassigned. However, the name of the layers was retained. The habitat and mode of life of Bositra has been debated for more than a century. There have been different interpretations, such as a pseudoplanktonic organism,[59] a benthic organism living on the open marine floor, where it was the main inhabitant of the basinal settings, and a hybrid mode, where it had a life cycle with holopelagic reproduction controlled by changes in oxygen levels, and even a chemosymbiotic lifestyle with the large crinoid rafts being the main “safe havens” to evade anoxic events. Various hypotheses along the years led to a large study in 1998, where the size/frequency distribution, the density of growth through lines related to the shell size and the position of the redox boundary by total organic carbon diagrams revealed that Bositra probably had a benthic mode of life.[60]
A pectinoidscallop. The presence of this genus along endobenthic and epibenthic bivalves, which are absent farther up the section, suggest a delayed overstepping of anoxic bottom waters on the Altdorf High.[61]
An inoceramidclam. Being the second most common genus of bivalve in the Formation, it has been subject to several studies in regards to its ecological niche, similar to Bositra. Several opinions include a pseudoplanktonic-only organism able to live in the open sea, or a benthic-only organism. Within the 1998 evaluation with Bositra, was found that this genus probably had a benthic juvenile stage that transitioned to a faculatively pseudoplanktonic adult.[60]
A coelodiscid sea snail. Is the oldest known holoplanktonic gastropod and the most abundant snail in the formation, thanks to a bilaterally symmetrical shell as an adaption to active swimming.[67]
A possible early Cuttlefish. It is one of the most important cephalopod fossils in the Sachrang Formation, due to having some of the earliest examples of pigments found on any species, also one of the first historically.[90] The pigments are preserved on various specimens with Eumelanin related to its ink sacs and including even phosphatized musculature.[10]
Type genus of Lioteuthididae inside Vampyromorphida. The taxonomic position of Lioteuthis is uncertain, although the fins reaching the proximal gladius section and the smooth median field suggest affinity to the Prototeuthididae[92]
A phylloceratidammonite. The largest ammonite found in the Posidonienschiefer comes from the Ohmden quarry, and is a specimen of Phylloceras heterophyllum with a diameter of 87cm.[71]
The specimen reported represents the oldest fossil record of an achelate larva, and the first representative of achelates in the Posidonia Shale. This larva shares similarities with the late Jurassic genus Cancrinos. It is also among the oldest examples of crustaceans which possibly could have lived as part of the plankton.[109]
California spiny lobsters are relatives of the Larval specimen from the Sachrang Formation
Type genus of the family Erymidae. Originally was placed within Glyphea as G. amalthei, informally used by Quenstedt and housed in the Museum Naturkunde in Württemberg. A series of later revisions proved it was a different genus.[113]
A coleiid decapod. The second largest decapod from the formation, P. giganteus, reaches a larger size than most other polychelidans, growing up to 15cm.[121]
A gregarious polychelidanLobster. specimens of Tonneleryon schweigerti were recovered generally in clusters of several individuals, due to that and the disposition of the specimens these probably represent mass-mortality assemblages and suggest this species was gregarious.[111]
An astacidean decapod of the family Uncinidae. Uncina posidoniae is among the largest known Jurassic crustaceans andis also the largest representative of the genus.[123]
The Largest complete Uncina posidoniae specimen, with 44 cm long.
Numerous disarticulated individuals, associated with fossil wood.[15]
A phosphatic-shelled barnacle of the family Eolepadidae.[15]Toarcolepas is provisionally interpreted as the oldest epiplanktonic barnacle known, and is thought to have lived attached to floating driftwood.[15]
Modern genus Lepas is among the closest related taxa to Toarcolepas
An Amphiesmenopteran of the family Necrotauliidae. The ovipositor terminalia of female N. parvulus indicate that these insects laid their eggs in soil rather than in water.
Lepidopterans probably related with the family Micropterygidae. Compared with their record in Grimmen, in Lower Saxony lepidopterans are rather scarce and badly preserved.
Extant member of Micropterygidae, Posidonia genera were probably similar
A primitive crane fly of the family Tanyderidae. Extant members of the family are nectar feeder while the diets of extinct members cannot be determined precisely.[162]
Extant member of Tanyderidae, Posidonia genera were probably similar
Echinoderm debris is relatively abundant in the shale-free Unken and Salzburg members, including crinoid and brittle star skeletal elements; sea urchins take their place later in the formation, with them having especially diversified at that time, leading to pedicellaria being observed very often.[40]
Various complete and nearly complete specimens, some associated with rafts.
Type genus of the family Pentacrinitidae. Like Seirocrinus, Pentacrinites formed colonies in rafting wood. Was a small genus, with multiple specimens no more than 1 meter long, usually measuring 40–70cm.
Close view in one specimen from the Posidonienschiefer
Exceptionally well preserved individual with the arms, pinnules and cirri largely intact
A crinoid in the family Isocrinida. This benthic crinoid clearly represents an exotic element in the typical Posidonia fauna, likely moved from coastal settings.
Various complete and nearly complete specimens, some associated with rafts
The largest known crinoid, from the family Pentacrinitidae. Seirocrinus consists of fossils in colonies along large wood trunks, with specimens up to 14 m long and the largest reaching 26 m, which makes it among the tallest known Mesozoic organisms, one of the largest invertebrates known in the fossil record and one if the tallest known animals.[171] It was an open ocean organism that lived on rafting wood, probably filtering food and serving as a refuge for other animals, such as ammonites. The crinoids had a large colonization process, based on their fossils in the wood.[172] The large rafts were the home for a high variety of marine organisms, such as barnacles, ammonites and others. It has been estimated that without the presence of modern raft wood predators (that appeared in the Bathonian) these rafts could have lasted up to 5 years, being the main reason that the crinoids were able to reach such huge sizes. The large rafts were also probably essential to distribute animals along the Early Jurassic seas.[13]
Close view of one specimen from the Posidonienschiefer
Type genus of the family Hybodontidae. It is the most abundant shark in the layers of the Sachrang Formation, with some of the best preserved specimens of the genus known.[179]
Hybodus Holzmaden specimen, among the best preserved of the genus, with belemmnites inside.
Anterior part of body with basicranium, palatoquadrates, Meckel's cartilage, ceratohyals, epihyals, teeth, traces of the branchial arches and the anterior finspine
A deep-bodied neopterygian, the type genus of the family Dapediidae. Unpublished material indicates the presence of one or even two more still undescribed species of Dapedium in the Lower Toarcian.[190][191]
A ganoin-scaled member of Ophiopsiformes (Halecomorphi). The type specimen is 51cm long, and has elongated and serrated body scales before the dorsal fin and tiny ganoid scales after it.[195]
Thousands of complete and nearly complete specimens
A member of the family Leptolepididae. The most common fish found within the formation, Leptolepis is thought to have formed large schools like modern herring.
A member of the family Leptolepididae. It was identified as Paraleptolepis, but this name is currently occupied by a Japanese fish genus of Early Cretaceous age.[201] It differs from Leptolepis coryphaenoides through the presence of a few autapomorphies and also in the retention of several primitive features not present on the former.[200] A relatively small fish, around 14cm long.[200]
The first ganoin-scaled member of Ophiopsiformes (Halecomorphi) from the Posidonienschiefer. Elongated morphology, with a length of ~39cm, covered by smooth, massive ganoin scales.[195]
Type member of the family Pachycormidae. A large representative of its family, reaching up to 1.5 m. One specimen preserves the stomach filled with numerous hooklets.[18]
A large coelacanth of the family Mawsoniidae.[214] The largest specimen known is GPIT.OS.770 (holotype), being over 1.6 m long.[213] The specimen preserves an ossified lung inside the abdominal cavity, and most of the body, being also one of the most complete coelacanths of the Jurassic found.[213][214]
A large ichthyosaur of the family Leptonectidae which, convergently with modern swordfish, evolved an extremely long upper jaw. Like these fishes, Eurhinosaurus is believed to be a fast swimming predator, able to hunt fish schools on same way. Large specimens of up to 6 m are known.
Likely a member of Parvipelvia, sister group to Stenopterygius + Ophthalmosauridae. A small- to mid-sized ichthyosaur, 2–3 m in length, with a relatively short and slender antorbital rostrum.[218]
A possible member of the family Leptonectidae. Most of the specimens of this genus have been referred to Leptonectes or Temnodontosaurus, although some remains in the Posidonienschiefer are too complex to be clearly referred.
An ichthyosaur of the family Stenopterygiidae. Magnipterygius may not have grown to a total length of much more than 120cm. It is therefore potentially only the second post-Triassic ichthyosaur known with such a small body size
Type genus of the family Stenopterygiidae. A common Toarcian ichthyosaur, present in multiple layers. The rather exquisite level of preservation has led to even the coloration being preserved. This shows a clear countershading, with an upper part being darker than the lower, similar to modern killer whales, the Heaviside's dolphin or the Dall's porpoise. There is also evidence of changes in color with ontogenetic changes, going from dark juveniles to countershaded adults. The skin was flexible & scaleless, as in dolphins.[222] The study of several specimens has revelated that Stenopterygius quadriscissus underwent a size-related trophic niche shift through ontogeny, shifting from a piscivorous diet to a teuthophagous diet, known thanks to exquisitely preserved stomach contents.[223]
Type genus of the family Temnodontosauridae. A large macroraptorial ichthyosaur, the apex predator of its environment. It ranges between 9 and 12 m, being one of the largest known ichthyosaurs, characterised by skulls and jaws over 1 m in length, with the largest being over 1.9 m long. It has been found with fragments of young ichthyosaurs in its stomach.[17]
SMNS 51945, an almost complete articulated skeleton lacking most of the skull
A plesiosauroid known from a well-preserved immature specimen with possible phosphatised muscle tissues and eumelanin that possibly corresponds to areas dark-coloured in life.[231]
Various complete and nearly complete specimens, one with soft tissue.[240]
A Plesiosauroidean that has been linked with Cryptoclididae, yet recently relocated as an indet position. Specimen MH 7 shows a mosaic of smooth skin and (possibly keeled) scales.[240]
An aquatic sphenodont of the family Pleurosauridae. Paleopleurosaurus shows a slight skeletal specialization for an aquatic lifestyle, achieved through the Jurassic gradually in pleurosaurs.[243]
Multiple specimens, referred/identified as turtles have been recovered, yet only the ones from Altdorf belong to a Testudine, with the pleurals resembling those of the genus Plesiochelys.[244] Other remains are either not catalogued or in private collections.[248]
A longirostrine thalattosuchian of the family Machimosauridae. Was considered synonymous with Steneosaurus until in 2020 the latter was recovered as invalid. It reached large sizes, with specimens exceeding 5 m, being a generalist predator.[251]
A mesorostrine thalattosuchian of the family Teleosauridae. A marine crocodylomorph with a diet probably composed of fish. Was considered synonymous with Steneosaurus until recently.[253] Due to the unusual placement of the external nares, Mystriosaurus was likely more terrestrial, or spent a greater amount of time on land, than other teleosauroids. This would explain its greater presence in zones of the formation closer to the emerged landmasses. Its morphology suggest it was a mesorostrine generalist.[253]
A thalattosuchian with a complex designation, probably the basalmost metriorhynchoid. Pelagosaurus typus was a small-bodied thalattosuchian (~1 m in length) considered to be an adept aquatic pursuit predator, with a long streamlined snout ideal for snapping at fast moving prey (one specimen was found with Leptolepis fishes inside) and large, anterolaterally placed orbits for increased visual acuity.[254]
A longirostrine thalattosuchian, the most basal known. Was considered synonymous with Steneosaurus. Longirostrine specialist, probably an active fish hunter.
A longirostrine thalattosuchian of the family Teleosauridae. Platysuchus was slightly more robust than its contemporaneous relatives, being probably adapted to hunt larger fish. It was a heavily armoured, semi-terrestrial longirostrine generalist form, indicated by the extensive and tightly packed rows of dorsal osteoderms.[251]
A rhamphorhynchine Pterosaur. It is one of the best known Early Jurassic pterosaurs.[257]Dorygnathus mistelgauensis is considered a junior synonym until more data can be recovered from the specimen, which is held in a private collection.[257] Soft tissues, including fur/feather-like filaments & possible coloration traces have been found.[260]
A rhamphorhynchine Pterosaur. Has been assigned to the genus Dorygnathus. It has an almost entirely complete skull which may help to explain the status of the genus Parapsicephalus.[261]
Right side of the skull, the right lower jaw, caudal vertebrae, neural arches, a radius, a metatarsal, a claw, fragments of ribs, scutes and plates.[262]
A basal member of Thyreophora. The compacted pile of disarticulated cranial and postcranial elements of the basal thyreophoran Emausaurus has been suspected to be a Speiballen (i.e., a compacted mass of indigestible stomach contents) regurgitated by a large marine reptile.[262]
Interpreted as representing a lateral osteoderm of the neck or shoulder region of an early diverging thyreophoran
Plantae
The Flora is dominated by horsetails, which may be in a similar ecological niche to the modern genus Phragmites, able to resist saline conditions. Storms or floods may be the major events that transported this flora to the sea.
The macroflora of the Posidonia Slate can be described as extremely poor in species.[267] Apart from the remains of horsetails, it is without exception the remains of coarse branches and fronds from gymnosperms, which can be assumed were transport resistant. Remains of ferns are completely missing, except for tall arboreal ferns (Peltaspermales).[268] Most of the flora was reported from the area of Braunschweig.[267] The major explanation for this flora could be that the plants in question are mono-or oligotypic stands on the edge of the waters that flowed into the Posidonienschiefer sea, probably torn away in flood events, easily fragmented during transport and from waves, especially in the occasional storm events postulated.[269] In terms of taphonomy, this would result in a comparison with today's reed Phragmites, which can form extensive stocks on the edge of shallow and slowly flowing waters.[267] The wood remnants clearly indicate higher diversity of coniferous flora in the delivery area than remains of leafy branches.[267] This fact is likely to be proportionate, similar to the frequent occurrence of charcoalized trunks, most of them are believed to be "driftwoods" which spent a long time drifting, and this also suggests frequent settlement with mussels and full-grown crinoids.[267][269] The deposition settings are a large distance from the nearest coastline (for southern Germany about 100 kilometers), making only plants resistant to transportation able to survive long enough to get deposited.[270][141] At Irlbach and Kheleim, NE of Regensburg, where the Posidonienschiefer has a near mainland deposit with abundant sand, a rich deposit filled with plant remains of different kinds (Seeds, reproductive organs, leaves, stems, cuticles and wood) with traces of coal was recovered, however, it was never studied in depth.[78] Of all the plant material excavated only a few bennettite leaves and two conifer branches with leaves were cited and none studied.[78] In the Austrian sites the Sachrang Member was developed in the basinal area, while the Unken Member, sandwiched between red, often condensed limestones, represents the marginal facies.[40] Due to being more marginal and connected with the southern Vindelician land, the most diverse palynological assemblages of the formation are found transported from zones with moldanuvian granites as proven by the feldspar accumulations.[40]
Phytoclasts
Phytoclasts have been recovered from several sections on the formation, but only studied in depth from the Dotternhausen and specially Dormettingen.[46] Here two kinds of phytoclasts were recovered, opaque phytoclasts (charcoal, indicator of wildfire activity on nearby landmasses, indicator of seasonal alterations of the water column) and translucent phytoclasts (indicator of proximal landmasses with high availability of wood and other plant material, as well as transport conditions).[46] On the lowermost part of the section opaque phytoclasts are low (15% of the total organic matter) while translucent are incredibly abundant (40%), lowering to around 20-10% on the next section.[46] The Exaratum subzone is the only one with an inverse trend and more abundance of opaque phytoclasts. On the Bifrons level, both types reach between a 15% and a 30%, showing a rapid increase, then decreasing at the end of the section to values of less than 10%.[46] Opaque Phytoclasts, for a supposed marine deposit are relatively abundant on some sections, while their decreasing levels suggest (along with increasing levels of Kaolinite) an increased delivery of land plant material by rivers, from areas with wetter climate and less frequent fires, while its rise suggests the opposite, a nearby continental setting with dry climate and continuous wildfire activity.[46]
Affinities with the families Peltaspermaceae, Corystospermaceae or Umkomasiaceae inside Peltaspermales. Pollen of uncertain provenance, that may be derived from any of the members of the Peltaspermales. The lack of distinctive characters and bad preservation are among the main factors making this palynological residue difficult to classify. arborescent to arbustive seed ferns.
Affinities with both Sciadopityaceae and Miroviaceae inside Pinopsida. This pollen's resemblance with extant Sciadopitys suggests that Miroviaceae may be an extinct lineage of sciadopityaceaous-like plants.[274]
Affinities with Cycadaceae and probably Cycadales. Alternatively it may be pollen from Bennettitales. It is the most abundant non-conifer pollen recovered from the formation, recovered in all the major sampled areas. Probably derived from arbustive cycads, this genus is related with dry settings, even being known from desertic regions.
Affinities with Cheirolepidiaceae inside Coniferae. Abundant in the Lower Jurassic of North and Southern Europe, represents pollen of medium to large arborescent plants, specially conifers. The abundance of pollen of Classopollis and other thermophilic plants was observed in this region in the lower Toarcian from the end of the antiquum (= tenuicostatum) zone to the middle of commune zone.[276]Classopollis is correlated with evaporites and are therefore associated with desert basins, but the shrubs may have also lived in xeric upland areas with seasonal fires. Evidence of fires is absent in the marine Posidonienschiefer, but has been recovered on the coeval nearshore calcareous sandstones.[276] It increases with the appearance of charcoal phytoclasts, as derived from dry settings with increased wildfires.[46]
Affinities with Gnetopsida and probably Gnetophyta. Has been considered pollen of Chloranthaceae. However, it is too old to belong to advanced angiosperms. It probably comes from cones related to the genus Piroconites kuesperti from the lowermost Jurassic of Germany, resembling pollen of extant Ephedra and Welwitschia.
Closer Look of Ephedra cones, a common gnetophyte. Clavatipollenites may come from a related plant
Affinities with Gleicheniaceae inside Gleicheniales. It suggests a relative increase of humidity on the rivers flowing towards the Austrian realm. The most abundant term spore in this region.
Affinities with the Cycadopsida inside Cycadales. Pollen related with modern Cycas, arbustive to lower floor plants, relatively abundant, present in various of the measured samples. The most common pollen of the Austrian realm, alongside being an indicator of dry settings.
Affinities with Selaginellaceae and probably Lycopsida. A rare element in the palynological records of the German Basin, although more abundant than any other spore recovered locally.
Affinities with the Pinidae inside Coniferae. Abundant in the Lower Jurassic of NW Europe. Its identification in the Posidonienschiefer is rather unclear due to the bad preservation of the pollen grains.
Affinities with the Ophioglossaceae inside Filicopsida. Spores related with modern floor ferns, which appear on abundant water locations. The Unken Member is considered a more basinal deposit, where wood and sporomorph remains are more common.
Affinities with Cheirolepidiaceae inside Pinaceae. Abundant in the Lower Jurassic of NW Europe. Spheripollenites co-occurs on the coeval Sorthat Formation with cuticles of Dactyletrophyllum ramonensis, and after further study a highly significant correlation was found, which may suggest that the species S. psilatus was produced by the conifer genus Dactyletrophyllum.[278]
Affinities with Equisetaceae inside Equisetopsida. A number of mostly very fragmented and not particularly well preserved, but clear horsetail remains have been described.[280][281]
Affinities with Umkomasiaceae or Corystospermaceae. The genus is based on bipinnate leaves, with a longitudinally striated rachis, a long petiole and secondary rachises.[283]
The only Pachypteris specimen known from the Sachrang Formation
Affinities with Ginkgoaceae inside Ginkgoales. In Germany, there are regular remains of coal, which are initially reminiscent of small ginkgo leaves. The leaves are hard to identify, more or less regularly concentric structures, with them sometimes appearing like the coarse fruiting bodies of wood-dwelling fungi, such as the genus Trametes.
Affinities with Araucariaceae or Cheirolepidiaceae inside Pinales. Pagiophyllum araucarinum predominates among the types of leafy coniferous branches found locally.
Widdringtonites liasicus specimen from the Sachrang Formation
Fossil wood
Fossil wood amount increases in the marginal Unken Member, with great amounts of logs and fragments more than 1 m long. Surface studies suggest relationships with the wood genera identified on the coeval Úrkút Manganese Ore Formation.[287]
Affinities with Araucariaceae inside Pinales. One of the largest known rafting wood specimens in the fossil record is assigned to this genus, with a length of 18 m.[14]
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