Papers by Michael Hautmann
Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen, 2024
This paper provides a palaeoecological analysis and interpretation of benthic marine communities ... more This paper provides a palaeoecological analysis and interpretation of benthic marine communities from the first two stages of the Jurassic in southern Germany, based on quantitative data that represent more than 1000 individuals from six samples. Alpha-diversity of these samples varies from eight to 48 species, with a tendency towards higher richness in the stratigraphically younger samples. Dominance (Simpson D) was relatively low in all samples, ranging from 0.06 to 0.24. In most samples, bivalves are the richest and most abundant taxon. The presence of gastropods is variable, ranging from complete absence to dominance in one sample (Betakalkbank; Sinemurian). Accessory taxa include brachiopods, crinoids and echinoids. The number of guilds varies from two to eleven; the most common guilds are epibyssally attached suspension feeders, semiinfaunal suspension feeders, reclining suspension feeders and locally epifaunal grazers/detritivores. Local factors that controlled the faunal composition include substratum, water depth and energy, and possibly oxygen content. However, cluster analysis also revealed a strong stratigraphic signal, which outweighs lithological similarities. We interpret this stratigraphic signal as a superordinated macroevolutionary pattern, which reflects the evolutionary changes that were associated with the recovery from the end-Triassic mass extinction. Based on the data from this paper, recovery lasted at least to Sinemurian, which is in accordance with bivalve diversity data from the UK. Globally, data on benthic recovery are still scarce, but it seems that there were notable differences among palaeogeographic regions. In comparison to the recovery from the end-Permian mass extinction, we found a less extreme change in richness and dominance, with neither a long lag phase nor an explosive diversification thereafter. We interpret this difference as a result of the lower extinction magnitude, which did not shatter the structure of marine benthos to the same extent than the end-Permian event did 50 Ma earlier.
Palaeontologische Zeitschrift, Dec 9, 2022
A reef-associated mollusc fauna (gastropods and bivalves) and its facies context are described fr... more A reef-associated mollusc fauna (gastropods and bivalves) and its facies context are described from latest Triassic (Sevatian-Rhaetian) reef carbonates of Austria (Rötelwand reef at Gaissau and Gosaukamm near Hallstatt). The studied carbonates from the Rötelwand reef consist of mollusc-rich rudstones, partly boundstones, which contain branched corals (Cycliphyllia and Retiophylia, Pinacophyllum), whereas coralline sponges are absent. The rich foraminiferid fauna that is associated with the reef builders consists of 11 genera; eight of these genera became extinct until the end of the Rhaetian. Associated with small patch reefs was a rich mollusc fauna with 19 gastropod species and 8 epifaunal bivalve species. The gastropod fauna is dominated by Microschiza rhaetica, Trochotoma praecursor, and the large growing Purpuroidea moosleitneri.
Papers in Palaeontology
Some 2.7 myr after the Permian–Triassic boundary mass extinction, a stepwise extinction of the ne... more Some 2.7 myr after the Permian–Triassic boundary mass extinction, a stepwise extinction of the nekton (ammonoids and conodonts) ended at the Smithian–Spathian boundary (SSB) during an episode of climate cooling. SSB records from continental shelves are usually affected by an unconformity, suggesting a forced regression of glacioeustatic origin. Here, we document a new 30-m-thick SSB section from Jebel Aweri (Batain Plain, Oman) that provides an exceptionally complete and expanded record preserved in an exotic block. Most of this SSB section consists of microbial boundstone build-ups with a framework of metazoan bioclasts that formed in shallow water on an offshore seamount. In Wadi Musjah (Hawasina nappes, Oman), another exotic block records the SSB in a deeper water setting represented by Hallstatt-type facies. These two sections provide a unique perspective on the early Spathian rapid re-diversification of conodonts. They led to a thorough revision of conodont taxonomy around the SSB and to the construction of the highest resolution biochronological scheme for this time interval in the Tethys. A total of five SSB sections from Oman representing both offshore seamounts and lower slope deposits were included in a high-resolution, quantitative unitary associations (UA) analysis. The resulting 8 conodont biozones are intercalibrated with ammonoid zones and with the carbonate carbon isotope record ultimately placing the SSB in the interval of separation between UAZ3 and UAZ4. Only the association of Novispathodus pingdingshanensis with Icriospathodus crassatus can be used to unambiguously characterize the base of the Spathian.
Freunde der Bayerischen Staatssammlung für Paläontologie und Geologie, Jahresbericht und Mitteilungen, 2023
Tropische Riffe gehören zu den vielfältigsten Ökosystemen der Erde. Die größte Diversität bzw. Ar... more Tropische Riffe gehören zu den vielfältigsten Ökosystemen der Erde. Die größte Diversität bzw. Artenzahl steckt allerdings weniger in den riffbildenden Organismen (z. B. Korallen, Schwämme) als in den riffbewohnenden Tieren und Pflanzen. Viele fossile Riffe hohen geologischen Alters sind massiv versteinert (lithifiziert) und ihre
Ablagerungen stark verändert (Diagenese), was u. a. Lösungsprozesse und Mineralneubildungen (Kalzitisierung und/oder Dolomitisierung) beinhaltet. Aus diesem Grund sind riffbewohnende Organismen selten gut erhalten. Sie fehlen häufig in der Dokumentation bzw. ihnen wird in wissenschaftlichen Studien keine besondere Bedeutung
beigemessen. Die Anwesenheit von Riffbewohnern in der Gesamtfauna findet dann nur kursorisch Erwähnung, die entsprechenden Arten werden in offener Nomenklatur, d. h. ohne genaue Artbestimmung, gelistet. Meistens werden solche riffbewohnenden Arten auch nicht abgebildet.
Eine neue Studie, erarbeitet von Wissenschaftlern der Bayerischen Staatssammlung für Paläontologie und Geologie München (NÜTZEL, NOSE), der Mineralogischen Staatssammlung München (HOCHLEITNER) und dem Paläontologischen Institut und Museum der
Universität Zürich (HAUTMANN), befasst sich mit fossilreichen obertriassischen Riffkalken des Rötelwand-Riffs, südöstlich Salzburg (Oberrhät-Riffkalk) und des Gosaukamms (Dachsteinkalk). Die mächtigen Kalke bauen dort, wie auch andernorts in den Nordalpen,
wesentliche Teile des Gebirges auf. Neben den sedimentologischen Aspekten zielt die Arbeit vor allem auf die Dokumentation der Riff-Fauna und hier insbesondere auf die riffbewohnenden Mollusken. Schnecken (Gastropoden) sind besonders häufig, mit z. T. auffällig großen Arten (z. B. Purporoidea moosleitneri NÜTZEL et al., 2022). Die Mollusken-
fauna ist Teil einer grobkörnigen Riffschutt-Fazies assoziiert mit kleinen Fleckenriffen, die im Falle des Rötelwand-Riffs fast ausschließlich aus grobästigen Steinkorallen (Cycliphyllia cyclica) aufgebaut sind. Gastropoden und Bivalven aus dem Oberrhät-Riffkalk finden sich in verschiedenen Museen und Privatsammlungen, wurden aber bislang
noch nicht eingehend untersucht, mit Ausnahme der Arbeiten von ZAPFE (1963, 1967). Ein weiteres Ziel dieser Studie ist die Bewertung des evolutiven Schicksals der riffbewohnenden Mollusken über das große Massenaussterben an der Trias-Jura-Grenze hinweg. Die hier vorgestellten Ergebnisse stellen eine deutschsprachige Zusammenfassung der in NÜTZEL et al. (2022) ausführlich publizierten Daten dar.
Earth-Science Reviews, Jul 1, 2015
A reduction in body size (Lilliput effect) has been repeatedly proposed for many marine organisms... more A reduction in body size (Lilliput effect) has been repeatedly proposed for many marine organisms in the aftermath of the Permian-Triassic (PT) mass extinction. Specifically-reduced maximum sizes of benthic marine invertebrates have been proposed for the entire Early Triassic. This concept was originally based on observations on Early Triassic gastropods from the western USA basin and the Dolomites (N Italy) and it stimulated subsequent studies on other taxonomic groups. However, only a few studies have tested the validity of the Lilliput effect in gastropods to determine whether the paucity of large-sized gastropods is a genuine signal or the result of a poor fossil record and insufficient sampling. In combination with a review of the literature, we document numerous new, abundant, large-sized gastropods from the Griesbachian outcrops of Greenland and from the Smithian-early Spathian interval in the southwestern USA. We show that large-sized ("Gulliver") gastropods (i) were present soon after the PT mass extinction, (ii) occurred in various basins, sedimentary facies and environmental contexts (from shallow to deeper settings), and (iii) belong to diverse higher-rank taxa. Focusing on the western USA basin, we investigate areas from which microgastropod shell-beds were previously presented as being typical. However, we show that Gulliver gastropods do occur in the very same areas. Insufficient sampling effort is probably the main reason for the rarity of reports of large Early Triassic gastropods, which is supported by preliminary rarefaction-based simulations. Finally, it appears that the recently documented middle to late Smithian climate shifts and the severe end-Smithian extinction of nekto-pelagic faunas did not reduce maximum shell sizes of gastropods.
Geobios, 2011
A single carbonate coquinoid lens from the Griesbachian (Early Triassic) of Shanggan, South China... more A single carbonate coquinoid lens from the Griesbachian (Early Triassic) of Shanggan, South China, yielded 11 bivalve species described in this study in addition to four gastropod and one ammonoid species reported elsewhere. This makes the Shanggan fauna one of the richest mollusc faunas from the early post-extinction interval after the end-Permian mass extinction event. Four of the present genera are long-term survivors, five are holdovers that went extinct at the end of the Griesbachian or later in the Early Triassic, and seven first appear in the Griesbachian. Three new bivalve species are described: Myalinella newelli nov. sp., Scythentolium scutigerulus nov. sp., and Eumorphotis shajingengi nov. sp. The genus Astartella, previously assumed to have vanished at the end of the Permian, is reported for the first time from the Early Triassic, which also removes Astartidae from Early Triassic Lazarus taxa. The small growth size of the Astartella specimens supports an earlier hypothesis that many of the Early Triassic Lazarus taxa did not survive in unknown refuges but were simply overlooked due to the scarcity of easily observable large-sized specimens. Ecologically, a comparatively high proportion of infaunal bivalve species (4/11) is remarkable for the early post-extinction interval, supporting the impression of a relatively advanced recovery state. Moreover, abundance-data of the bivalve-gastropod community reveal a remarkably low dominance index (D = 0.17) that is suggestive for advanced recovery and stable environmental conditions. It is proposed that the Shanggan fauna represents a late Griesbachian benthic recovery event that coincided with the appearance of similarly diverse benthic faunas in Oman and Primorye. A high proportion of genera that have previously not been reported from the Early Triassic indicate that the prevalence of poor preservation conditions is a major obstacle in identifying early phases of recovery from the greatest crisis in the history of metazoan life. The early recovery of benthic faunas reported in this study questions previous claims of a prolonged lag phase as a consequence of the extraordinary extinction magnitude or the persistence of adverse environmental conditions.
Palaeontology, Dec 9, 2019
Definitions of macroevolution fall into three categories: (1) evolution of taxa of supraspecific ... more Definitions of macroevolution fall into three categories: (1) evolution of taxa of supraspecific rank; (2) evolution on the grand timescale ; and (3) evolution that is guided by sorting of interspecific variation (as opposed to sorting of intraspecific variation in microevolution). Here, it is argued that only definition 3 allows for a consistent separation of macroevolution and microevolution. Using this definition, speciation has both microevolutionary and macroevolutionary aspects: the process of morphological transformation is microevolutionary, but the variation among species that it produces is macroevolutionary, as is the rate at which speciation occurs. Selective agents may have differential effects on intraspecific and interspecific variation, with three possible situations: effect at one level only, effect at both levels with the same polarity but potentially different intensity, and effects that oppose between levels. Whereas the impact of all selective agents is direct in macroevolution, microevolution requires intraspecific competition as a mediator between selective agents and evolutionary responses. This mediating role of intraspecific competition occurs in the presence of sexual reproduction and has therefore no analogue at the macroevolutionary level where species are the evolutionary units. Competition between species manifests both on the microevolutionary and macroevolutionary level, but with different effects. In microevolution, interspecific competition spurs evolutionary divergence, whereas it is a potential driver of extinction at the macroevolutionary level. Recasting the Red Queen hypothesis in a macroevolutionary framework suggests that the effects of interspecific competition result in a positive correlation between origination and extinction rates, confirming empirical observations herein referred to as Stanley's rule.
Swiss Journal of Geosciences, Mar 16, 2011
A well-preserved ammonoid fauna of Early Dienerian age has long been known from the lower portion... more A well-preserved ammonoid fauna of Early Dienerian age has long been known from the lower portion of the Candelaria Formation in the old Candelaria silver mining district in Mineral and Esmeralda Counties, Nevada, but for a number of reasons, this fauna has never been studied in detail nor illustrated. Previous authors assigned this ammonoid fauna to the Early Dienerian Proptychites candidus Zone of Canada. In reality, it more closely resembles the Tethyan faunas than the higher palaeolatitude Canadian faunas, thus indicating the presence of some degree of equatorial faunal exchange between opposite sides of the Panthalassic Ocean during Early Dienerian time. It also indicates the onset of a provincialism, which contrasts with the cosmopolitan Griesbachian faunas. A rigorous taxonomic analysis of the Candelaria fauna allows us to differentiate the following ten species, which include two new species and one new genus (Mullericeras nov. gen.) belonging to the new family Mullericeratidae: Ambites lilangensis (KRAFFT, 1909),
Palaeontology, Jul 28, 2015
Changes of community structure in response to competition usually take place on timescales that a... more Changes of community structure in response to competition usually take place on timescales that are much too short to be visible in the geological record. Here we report the notable exception of a benthic marine community in the wake of the end-Permian mass extinction, which is associated with the microbial limestone facies of the earliest Triassic of South China. The newly reported fauna is well preserved and extraordinarily rich (30 benthic macroinvertebrate species, including the new species Astartella? stefaniae (Bivalvia) and Eucochlis obliquecostata (Gastropoda)) and stems from an environmentally stable setting providing favourable conditions for benthic organisms. Whereas changes in the taxonomic composition are negligible over the observed time interval of 10-100 ka, three ecological stages are identified, in which relative abundances of initially rare species continuously increased at the cost of previously dominant species. Concomitant with the changes of dominant species is an increase in faunal evenness and hetero
Palaeogeography, Palaeoclimatology, Palaeoecology, Oct 1, 2011
New ichnological data from the Lower Triassic Werfen Formation (Dolomites, Italy) revealed an une... more New ichnological data from the Lower Triassic Werfen Formation (Dolomites, Italy) revealed an unexpectedly diverse and complex ichnofauna in mixed siliclastic-carbonate shelf sediments of the western tropical Tethys shortly after the end-Permian mass extinction event. Common elements are Thalassinoides, Palaeophycus and Planolites. Other associated ichnogenera include Spongeliomorpha, Rhizocorallium, Lockeia, Catenichnus, Helminthopsis, and Taenidium. One structure is tentatively determined as Curvolithus. Biostratigraphic data (conodonts and bivalves) of the trace fossil interval (lower Seis/Siusi Member) suggest a late Griesbachian age, less than 1 Ma after the end-Permian mass extinction event. Similarly diverse ichnofossil communities from this time interval have recently been described from the Boreal Realm, but this is the first record of a diverse Griesbachian ichnoassemblage from the tropics, indicating that the early recovery of trace fossil producers was not latitudinally restricted, as previously proposed. Accordingly, relatively advanced recovery stages were reached on a global scale much earlier than the Spathian as is commonly acknowledged. The early and interregional peak in ichnofaunal recovery implies subsequent ecological setbacks in post-Griesbachian times that explain the overall delay of benthic recovery until the Spathian. Rather than persistent catastrophic conditions during the Griesbachian, a global and synchronous succession of crises and relaxation phases after the Griesbachian is proposed as an explanatory model for the recovery pattern of benthic ecosystems.
Journal of Paleontology, Oct 9, 2020
We describe two new genera of Triassic Aviculopectinoidea: Cristaflabellum n. gen., which is bico... more We describe two new genera of Triassic Aviculopectinoidea: Cristaflabellum n. gen., which is biconvex and has a strongly plicate shell, and Globodiscus n. gen., which is equiconvex and externally smooth or nearly so. Globodiscus contains the new species G. kiliani n. gen. n. sp. and G. vinzenti n. gen. n. sp. In order to make the taxonomic concept of the superfamily Aviculopectinoidea more consistent with that of its sister group Pectinoidea (scallops), we use tribes rather than families or subfamilies for accommodating the new taxa. Cristaflabellum is placed in the tribe Antijanirini (previously family Antijaniridae), whereas Globodiscus is made the type genus of the new tribe Globodiscini. Both tribes are placed within the family Aviculopectinidae, which is revised to include both equiconvex and inequiconvex taxa. We suggest that tribes are a more appropriate taxonomic rank for many of the previously erected species-poor families and subfamilies of Aviculopectinoidea. UUID: http://zoobank.org/d143663a-9016-459f-8e24-660102adcf6a
Swiss Journal of Palaeontology, Apr 18, 2022
The impact of increasing atmospheric CO 2 and the resulting decreasing pH of seawater are in the ... more The impact of increasing atmospheric CO 2 and the resulting decreasing pH of seawater are in the focus of current environmental research. These factors cause problems for marine calcifiers such as reduced calcification rates and the dissolution of calcareous skeletons. While the impact on recent organisms is well established, little is known about long-term evolutionary consequences. Here, we assessed whether ammonoids reacted to environmental change by changing septal thickness. We measured the septal thickness of ammonoid phragmocones through ontogeny in order to test the hypothesis that atmospheric pCO 2 , seawater pH and other factors affected aragonite biomineralisation in ammonoids. Particularly, we studied septal thickness of ammonoids before and after the ocean acidification event in the latest Triassic until the Early Cretaceous. Early Jurassic ammonoid lineages had thinner septa relative to diameter than their Late Triassic relatives, which we tentatively interpret as consequence of a positive selection for reduced shell material as an evolutionary response to this ocean acidification event. This response was preserved within several lineages among the Early Jurassic descendants of these ammonoids. By contrast, we did not find a significant correlation between septal thickness and long-term atmospheric pCO 2 or seawater pH, but we discovered a correlation with palaeolatitude.
Neues Jahrbuch für Geologie und Paläontologie, Apr 7, 2003
ABSTRACT Myophoria woehrmanni, which was erroneously identified as Cardita decussata by W OHRMANN... more ABSTRACT Myophoria woehrmanni, which was erroneously identified as Cardita decussata by W OHRMANN (1889), is designated as type-species of Gruenewaldia. Gruenewaldia is separated from the morphologically similar genus Elegantinia by the lack of a posterior elongation of its central tooth (2) in the left valve. Discussion of the somewhat ambiguous character pattern of Gruenewaldia leads to corro-boration of its conventional assignment to the Myophoriidae. The development of strong pedal muscles, reflected by corresponding modifications of the shell, is an important evolutionary novelty of the Trigoniidae and a major difference to Gruenewaldia. The new findings are summarized in a revised diagnosis of Gruene-waldia. Zusammenfassung: Als Typusart der Gattung Gruenewaldia wird Myophoria woehrmanni gewahlt, die von W OHRMANN (1889) irrtiimlicherweise als Cardita decussata bestimmt worden war. Gruenewaldia unterscheidet sich von der ahnlichcn Gattung Elegantinia durch das Fehlen einer leistenformigen hinteren Verlangerung des zentralen Zahns (2) der linken Klappe. Die An-oder Abwesenheit radialer Rippen auf der Latera ist dagegen taxonomisch weniger signifikant. Bei einigen Arten der Gattung Gruenewaldia, einschlieBlich der Typusart, sind samtliche Schlosszahne gerieft, bei anderen dagegen die Zahne 3b und 4 a nur auf ihren Innen-flanken. Obwohl das Merkmalsmuster von Gruenewaldia einen gewissen Inter-pretationsspielraum laBt, ergibt sich aus Abwagung der Signifikanz der einzelnen Merkmale eine Bestatigung der konventionellen Zuordnung zur Familie Myo-phoriidae. Die Entwicklung starker Pedalmuskeln, die auch Veranderungcn in der Morphologie der Klappen mit sich brachte, wird als wichtige evolutive Neu-erwerbung der Trigoniidae angesehen, die Gruenewaldia fehlt. Die neuen Ergebnisse werden in einer revidierten Diagnose von Gruenewaldia zusammengefasst.
Scientific Reports, Oct 4, 2021
The mass extinction characterizing the Permian/Triassic boundary (PTB; ~ 252 Ma) corresponds to a... more The mass extinction characterizing the Permian/Triassic boundary (PTB; ~ 252 Ma) corresponds to a major faunal shift between the Palaeozoic and the Modern evolutionary fauna. The temporal, spatial, environmental, and ecological dynamics of the associated biotic recovery remain highly debated, partly due to the scarce, or poorly-known, Early Triassic fossil record. Recently, an exceptionally complex ecosystem dated from immediately after the Smithian/Spathian boundary (~ 3 myr after the PTB) was reported: the Paris Biota (Idaho, USA). However, the spatiotemporal representativeness of this unique assemblage remained questionable as it was hitherto only reported from a single site. Here we describe three new exceptionally diverse assemblages of the same age as the Paris Biota, and a fourth younger one. They are located in Idaho and Nevada, and are taxonomic subsets of the Paris Biota. We show that the latter covered a region-wide area and persisted at least partially throughout the Spathian. The presence of a well-established marine fauna such as the Paris Biota, as soon as the early Spathian, indicates that the post-PTB biotic recovery and the installation of complex ecosystems probably took place earlier than often assumed, at least at a regional scale. At the Permian/Triassic boundary (PTB; ~ 252 Ma), the most severe Phanerozoic mass extinction led to the disappearance of over 80% of marine genera 1,2. This event constitutes a crucial turning point in the history of life, marking the transition from the Paleozoic to the Modern evolutionary fauna 3. It is now acknowledged that this transition did not only result from the PTB crisis, but also from the combined effects of several successive smaller-scale environmental and biotic crises during the Early Triassic 4-7. These events are often assumed to have significantly delayed the post-PTB biotic recovery that is thought to have only started late in the Early Triassic, and been fully completed by the Middle Triassic 8-11. However, rich Early Triassic fossiliferous assemblages exhibiting relatively diversified marine communities are rare 12,13 , leaving very few clues to unveil the processes underlying the post-PTB biotic recovery. Until recently, the oldest known complex and diversified marine ecosystem following the PTB was the Luoping Biota from the Anisian (early Middle Triassic; ca. 10 myr after the PTB) of South China 14. However, Brayard et al. 15 reported a complex, diversified and exceptionally-preserved Early Triassic fossil assemblage from Paris Canyon, southeastern Idaho, USA, named the Paris Biota. Dated from immediately after the Smithian/Spathian boundary (SSB; ~ 249.2 Ma 16), this biota provides a novel window on Early Triassic ecosystems. Its relative high diversity and ecological complexity is all the more remarkable as the late Smithian corresponds to a severe secondary extinction for nekto-pelagic organisms 17-20 , associated with a marked and rapid change from warm to
Geology, 2011
We are pleased that our study prompted Fraiser et al. (2010) to abandon their previous concept of... more We are pleased that our study prompted Fraiser et al. (2010) to abandon their previous concept of a global Early Triassic "Lilliput effect" that extended from the Griesbachian to at least the Smithian (e.g., Fraiser and Bottjer, 2004). As far as we know, their view that the Lilliput effect was restricted to just the fi rst two Early Triassic conodont zones is expressed in their Comment for the fi rst time. Indeed, Twitchett's (2007) conclusion cited in Fraiser et al. (2010) explicitly assumed that "pre-extinction sizes are not commonly recorded until at least the Middle Triassic" (p. 132). Additionally, Twitchett concluded that "all animal groups suffered a size reduction after the Late Permian extinction event" (p. 143), a conclusion that is contradicted by the well-known normal size of ammonoids. Furthermore, the distinction between a Lilliput phase spanning the earliest Triassic zones and a subsequent phase spanning the rest of the Early Triassic with still-reduced body size is arbitrary. Even Twitchett (2007) stated that the Lilliput effect sensu stricto is not applicable for gastropods at the Permian-Triassic boundary because boundary-crossers have not yet been reported among gastropod species. The Lilliput effect sensu lato has been considered by various authors (including our opponents; e.g., Twitchett, 2007), based on the comparisons of size distributions of pre-and post-crisis gastropod faunas (without discrimination of taxa). In this case, it is irrelevant whether newly originated taxa are included because such comparisons argue on the class and sample level. On that basis, a small body size was suggested to be typical for Gastropoda during the entire Early Triassic (e.g., Fraiser and Bottjer, 2004). The dominance of small gastropods is not unique to the Early Triassic; this size class is largely dominant in Recent normal marine faunas (Bouchet et al., 2002; 71.4% of the species are <19 mm) and most fossil faunas throughout the Phanerozoic. It is only the apparent lack of very large gastropods in the Early Triassic which is remarkable. This alleged small maximum size of Early Triassic gastropods also plays an important role in the papers of Fraiser and Bottjer (2004, p. 267) and Twitchett (2007, his table 1). The discovery of gastropods that are twice as large (~100 mm) as previously known is relevant. Gastropods with a size of 20-40 mm have repeatedly been reported from Early Triassic faunas, including the Griesbachian (Brayard et al., 2010), not only in high latitudes (as argued by Fraiser et al., 2010) but also in low latitudes (37-mm-wide Naticopsis from Oman, a large size for gastropods; only ~10% of Bouchet et al.'s [2002] species show adult size >37 mm). The largest known gastropod ever (Syrinx aruanus) mentioned by Fraiser et al. (2010) is a recent neogastropod, a group originating in the Gastropod evidence against the Early Triassic Lilliput effect: REPLY
eLS, Aug 15, 2012
One of the five greatest mass extinction events in Earth's history occurred at the end of the... more One of the five greatest mass extinction events in Earth's history occurred at the end of the Triassic, c. 200 million years ago. This event ultimately eliminated conodonts and nearly annihilated corals, sphinctozoan sponges and ammonoids. Other strongly affected marine taxa include brachiopods, bivalves, gastropods and foraminifers. On the land, there is evidence for a temporal disturbance of plant communities but only few plant taxa finally disappeared. Terrestrial vertebrates also suffered but timing and extent of this extinction remains equivocal. The cause of the end-Triassic mass extinction was probably linked to the contemporary activity of the Central Atlantic Magmatic Province, which heralded the breakup of the supercontinent Pangaea. Possible kill mechanisms associated with magmatic activity include sea-level changes, marina anoxia, climatic changes, release of toxic compounds and acidification of seawater. Remarkably, long-term effects on marine biota were rather different between ecological groups: a nearly instantaneous recovery of level-bottom communities is contrasted by the virtual absence of reef systems for nearly 10 million years after the extinction event. Key Concepts: Nearly half of all marine genera and a smaller but still significant proportion of terrestrial taxa went extinct at the end of the Triassic period, c.200 million years ago. The end-Triassic mass extinction took place during a geologically short time interval, which coincided with the onset of massive magmatic extrusions along fracture zones of the disassembling supercontinent Pangaea. A cause-and-effect relationship between magmatic activity and mass extinction is indicated by the accordance of predicted extinction patterns and observed data from the fossil record. Ocean acidification as a kill mechanism in marine ecosystems is confirmed by preferential extinction of taxa with thick aragonitic skeletons. The end-Triassic mass extinction event provides a test-case for studying evolutionary responses to major environmental disturbances on the global scale and over geological time. Although there are differences in emission rates, the massive magmatic CO2 release at the end of the Triassic is quantitatively similar to a potential release by complete combustion of the global fossil fuel reserves. A provisional prediction from the data of the fossil record is that in the marine realm level-bottom communities are able to recover much more quickly from the effects of excess CO2 than reef systems. Keywords: mass extinction; Triassic; Jurassic; volcanism; reefs; level-bottom communities; climatic change; ocean acidification
Journal of Molluscan Studies, Jun 7, 2017
Ammonoids that lived in the wake of the end-Permian mass extinction are frequently encrusted by t... more Ammonoids that lived in the wake of the end-Permian mass extinction are frequently encrusted by the shells of cementing bivalves, but the majority of these epizoans are too poorly preserved for a precise taxonomic identification. However, our huge collection of Griesbachian-Dienerian (Early Triassic, c. 252-251 Ma) ammonoids from east Greenland, the Salt Range (Pakistan) and Spiti (India) includes three ammonoid specimens with epizoans that can reliably be identified as oysters, based on their attachment by the left valve and the morphology of their ligament area. Some of these oysters have their right (upper) valve preserved, which shows the characteristic morphology of Liostrea. These finds predate (1) the previously known first occurrence of oysters by c. 5 Myr, (2) that of Gryphaeidae by c. 15 Myr and (3) that of Liostrea by c. 20 Myr. Moreover, the stratigraphic polarity indicates that Liostrea is a candidate ancestor of Gryphaea and not vice versa. The open-marine habitat of the Liostrea epizoans described herein provides an explanation for the unusual ecology of its putative descendent Gryphaea as a fully marine soft-bottom dweller with a preference for relatively deep water environments during the Triassic. The revised timing of the early phylogeny of oysters suggests that this bivalve clade underwent rapid morphological divergence during the initial phase of its evolution.
Journal of Paleontology, May 1, 2008
The Mysidiellidae are morphologically isolated among Triassic bivalves but share important charac... more The Mysidiellidae are morphologically isolated among Triassic bivalves but share important characters with Late Paleozoic Ambonychioidea. Apart from a great similarity in the general shape of the shell, the most primitive mysidiellid genus Promysidiella resembles ambonychioids in the presence of a duplivincular-opisthodetic ligament system. Within the Mysidiellidae, this ligament type evolved into the transitional ligament system that characterizes Late Triassic Mysidiella. The phyletic polarity indicates that this evolution probably took place by paedomorphosis. New examinations of the shell microstructure of Mysidiella demonstrate the presence of simple prismatic and possibly foliated structures in the calcitic outer shell layer, which further supports an ambonychioid affinity. Therefore, the Mysidiellidae are removed from the Mytiloidea and assigned to the Ambonychioidea. The poorly known genus Protopis, which was originally included in the Mysidiellidae, probably had a parivincular ligament system and was hence a member of the Heteroconchia. Joannina, which was previously considered a junior synonym of Protopis, is re-established. The hinge margin of Joannina carries a well developed nymph but lacks teeth. These characters as well as its modioliform shape, anterior shell lobe, and pronounced diagonal carina link Joannina with the Late Triassic genus Healeya (Modiomorphoidea). Both taxa are herein placed in the new family Healeyidae, which differs from the morphologically similar Kalenteridae in the absence of elaborated hinge teeth. Protopis, as well as the recently described genera Leidapoconcha, Waijiaoella, and Qingyaniola, are tentatively assigned to the Healeyidae.
Lethaia, Jul 31, 2018
A new Early Triassic marine fauna is described from an exotic block (olistolith) from the Ad Daff... more A new Early Triassic marine fauna is described from an exotic block (olistolith) from the Ad Daffah conglomerate in eastern Oman (Batain), which provides new insights into the ecology and diversity during the early aftermath of the Permian-Triassic Boundary mass extinction. Based on conodont quantitative biochronology, we assign a middle Griesbachian age to the upper part of this boulder. It was derived from an offshore seamount and yielded both nektonic and benthic faunas, including conodonts, ammonoids, gastropods and crinoid ossicles in mass abundance. This demonstrates that despite the stratigraphically near extinction at the Permian-Triassic Boundary, Crinoidea produced enough biomass to form crinoidal limestone as early as middle Griesbachian time. Baudicrinus, previously placed in Dadocrinidae, is now placed in Holocrinidae; therefore, Dadocrinidae are absent in the Early Triassic, and Holocrinidae remains the most basal crown-group articulates, originating during the middle Griesbachian in the Tethyan Realm. Abundant gastropods assigned to Naticopsis reached a shell size larger than 20 mm and provide another example against any generalized Lilliput effect during the Griesbachian. Whereas the benthic biomass was as high as to allow the resumption of small carbonate factories, the taxonomic diversity of the benthos remained low compared to post-Early Triassic times. This slow benthic taxonomic recovery is here attributed to low competition within impoverished post-extinction faunas. □ benthos, biotic recovery, Griesbachian, Oman, Permian-Triassic Boundary.
Palaeontology, Nov 1, 2005
The heterodont bivalve Sinbadiella pygmaea gen. et sp. nov. is described from the Sinbad Limeston... more The heterodont bivalve Sinbadiella pygmaea gen. et sp. nov. is described from the Sinbad Limestone Member (Olenekian, Smithian) of the Lower Triassic Moenkopi Formation of Utah (USA). The new taxon is tentatively assigned to the Lucinidae on the grounds of its external morphology, larval shell morphology and hinge characters. It is the only definite representative of the Superorder Heterodonta in the Olenekian, removing this major clade of bivalves from the long list of Early Triassic Lazarus taxa. Although at least locally very abundant, the new taxon has been overlooked by earlier workers, probably due to its minute size. Dwarfism is a widespread phenomenon in Early Triassic faunas, which has been attributed to ongoing reduction of primary production. If S. pygmaea was a lucinid, a chemosymbiotic feeding mode can be inferred, which might explain why it was able to thrive in conditions that suppressed filter feeding heterodonts.
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Papers by Michael Hautmann
Ablagerungen stark verändert (Diagenese), was u. a. Lösungsprozesse und Mineralneubildungen (Kalzitisierung und/oder Dolomitisierung) beinhaltet. Aus diesem Grund sind riffbewohnende Organismen selten gut erhalten. Sie fehlen häufig in der Dokumentation bzw. ihnen wird in wissenschaftlichen Studien keine besondere Bedeutung
beigemessen. Die Anwesenheit von Riffbewohnern in der Gesamtfauna findet dann nur kursorisch Erwähnung, die entsprechenden Arten werden in offener Nomenklatur, d. h. ohne genaue Artbestimmung, gelistet. Meistens werden solche riffbewohnenden Arten auch nicht abgebildet.
Eine neue Studie, erarbeitet von Wissenschaftlern der Bayerischen Staatssammlung für Paläontologie und Geologie München (NÜTZEL, NOSE), der Mineralogischen Staatssammlung München (HOCHLEITNER) und dem Paläontologischen Institut und Museum der
Universität Zürich (HAUTMANN), befasst sich mit fossilreichen obertriassischen Riffkalken des Rötelwand-Riffs, südöstlich Salzburg (Oberrhät-Riffkalk) und des Gosaukamms (Dachsteinkalk). Die mächtigen Kalke bauen dort, wie auch andernorts in den Nordalpen,
wesentliche Teile des Gebirges auf. Neben den sedimentologischen Aspekten zielt die Arbeit vor allem auf die Dokumentation der Riff-Fauna und hier insbesondere auf die riffbewohnenden Mollusken. Schnecken (Gastropoden) sind besonders häufig, mit z. T. auffällig großen Arten (z. B. Purporoidea moosleitneri NÜTZEL et al., 2022). Die Mollusken-
fauna ist Teil einer grobkörnigen Riffschutt-Fazies assoziiert mit kleinen Fleckenriffen, die im Falle des Rötelwand-Riffs fast ausschließlich aus grobästigen Steinkorallen (Cycliphyllia cyclica) aufgebaut sind. Gastropoden und Bivalven aus dem Oberrhät-Riffkalk finden sich in verschiedenen Museen und Privatsammlungen, wurden aber bislang
noch nicht eingehend untersucht, mit Ausnahme der Arbeiten von ZAPFE (1963, 1967). Ein weiteres Ziel dieser Studie ist die Bewertung des evolutiven Schicksals der riffbewohnenden Mollusken über das große Massenaussterben an der Trias-Jura-Grenze hinweg. Die hier vorgestellten Ergebnisse stellen eine deutschsprachige Zusammenfassung der in NÜTZEL et al. (2022) ausführlich publizierten Daten dar.
Ablagerungen stark verändert (Diagenese), was u. a. Lösungsprozesse und Mineralneubildungen (Kalzitisierung und/oder Dolomitisierung) beinhaltet. Aus diesem Grund sind riffbewohnende Organismen selten gut erhalten. Sie fehlen häufig in der Dokumentation bzw. ihnen wird in wissenschaftlichen Studien keine besondere Bedeutung
beigemessen. Die Anwesenheit von Riffbewohnern in der Gesamtfauna findet dann nur kursorisch Erwähnung, die entsprechenden Arten werden in offener Nomenklatur, d. h. ohne genaue Artbestimmung, gelistet. Meistens werden solche riffbewohnenden Arten auch nicht abgebildet.
Eine neue Studie, erarbeitet von Wissenschaftlern der Bayerischen Staatssammlung für Paläontologie und Geologie München (NÜTZEL, NOSE), der Mineralogischen Staatssammlung München (HOCHLEITNER) und dem Paläontologischen Institut und Museum der
Universität Zürich (HAUTMANN), befasst sich mit fossilreichen obertriassischen Riffkalken des Rötelwand-Riffs, südöstlich Salzburg (Oberrhät-Riffkalk) und des Gosaukamms (Dachsteinkalk). Die mächtigen Kalke bauen dort, wie auch andernorts in den Nordalpen,
wesentliche Teile des Gebirges auf. Neben den sedimentologischen Aspekten zielt die Arbeit vor allem auf die Dokumentation der Riff-Fauna und hier insbesondere auf die riffbewohnenden Mollusken. Schnecken (Gastropoden) sind besonders häufig, mit z. T. auffällig großen Arten (z. B. Purporoidea moosleitneri NÜTZEL et al., 2022). Die Mollusken-
fauna ist Teil einer grobkörnigen Riffschutt-Fazies assoziiert mit kleinen Fleckenriffen, die im Falle des Rötelwand-Riffs fast ausschließlich aus grobästigen Steinkorallen (Cycliphyllia cyclica) aufgebaut sind. Gastropoden und Bivalven aus dem Oberrhät-Riffkalk finden sich in verschiedenen Museen und Privatsammlungen, wurden aber bislang
noch nicht eingehend untersucht, mit Ausnahme der Arbeiten von ZAPFE (1963, 1967). Ein weiteres Ziel dieser Studie ist die Bewertung des evolutiven Schicksals der riffbewohnenden Mollusken über das große Massenaussterben an der Trias-Jura-Grenze hinweg. Die hier vorgestellten Ergebnisse stellen eine deutschsprachige Zusammenfassung der in NÜTZEL et al. (2022) ausführlich publizierten Daten dar.