Ammonoids at the Triassic-Jurassic Transition: Pulling Back from the Edge of Extinction The Triassic-Jurassic (T-J) extinction significantly affected the evolutionary history of the ammonoids. We use high level taxonomic changes, patterns of generic diversity and differences in morphospa...

Chapter 2.18 by Longridge & Smith on #Ammonoids at the #Triassic-Jurassic Transition: Pulling Back from the Edge of #Extinction: rdcu.be/eQR8J

Latest underline a clear impact on #morphology although the reasons remain elusive: doi.org/10.1111/pala... doi.org/10.1093/iob/...
doi.org/10.1016/j.ge...

Taxonomic Diversity and Morphological Disparity of Paleozoic Ammonoids The Ammonoidea are well represented in terms of numbers of species over a large range of time and they have survived many extinction events. The time interval from the Early Devonian through to the Tr...

Chapter 2.16 by Korn et al. on Taxonomic #Diversity and Morphological #Disparity of #Paleozoic #Ammonoids: rdcu.be/eQH2S

Latest lacking early disparity burst (doi.org/10.1126/scia...) suggestive of passive life history or too conservative methods:
doi.org/10.1017/pab....
dx.doi.org/10.4202/app....

View of an Ammonoids fossil from the outside. The fossil surface shimmers in metallic golden colour from Pyrite coating. Height of fossil: 2cm / ¾inch

An Ammonoids fossil cut in half and polished.

⛏ Midweek geology ⚒

❓ How do Ammonoids look inside?
-》Let's ✂️ & 👀

👉 Ammonoids lived in the world oceans for ~350 million years from early Devonian until the extinction of the Dinosaurs 66my ago.

🔎 Outside of an #Ammonoids #fossil (left) & one with polished inside (right) 👇

Biostratigraphy of Triassic Ammonoids The Triassic is a turning point in the evolutionary history of ammonoids, characterized by the flourishing Ceratitida and the appearance of the first heteromorphs. Following the end-Permian mass extin...

Chapter 2.13 by Jenks et al. on #Biostratigraphy of #Triassic #Ammonoids: rdcu.be/eNqBl

Additional progress has been made particularly in the Early Triassic:
doi.org/10.1016/j.ea...
doi.org/10.1016/j.ge...
but also in the Middle to Late Triassic:
doi.org/10.17738/aje...
doi.org/10.1007/978-...

Fig. 1. Palaeo-location of the 27 regions of A) conodont and B) ammonoid taxa taxa defined in this study, respectively. Each region is associated to its number of sampled localities encircled by five arcs, each arc corresponding to a time interval (Changhsingian, Griesbachian, Dienerian, Smithian, or Spathian). A coloured arc means that the region includes at least one locality dated from this time interval; an unfilled arc means that the region does not include any locality dated from this time interval. See the section Material and methods for details about the calculation of the palaeocoordinates. Silhouettes of conodont and ammonoid are public-domain images from the Phylopic website (compare https://doi.org/10.18261/let.58.3.2).

Values of Dispersal-Niche Continuum Index (DNCI) show ammonoid biogeography was dispersal-constrained in Griensbachian and Spathian as opposed to niche constrained in the Smithian, while conodonts were more functionally (niche) constrained in Griesbachian as opposed to driven by both niche and dispersal constraints from the Dienerian to Spathian. Black dots and associated horizontal black lines represent mean value and ±2 standard error, respectively.

Biogeography after #Permian #Triassic boundary crisis resulted from a complex combination of functional and dispersal mechanisms doi.org/10.18261/let...

#Ammonoids limited by #dispersal in Griesbachian/Spathian, by niche in Smithian; #conodonts by #niche in Griesbachian, mixed in Dienerian–Spathian

Ammonoids and Quantitative Biochronology—A Unitary Association Perspective Ammonoid evolutionary changes have long been recognized to be excellent time markers. They are the major macrofossil group to date and correlate Paleozoic and Mesozoic marine strata. Originations and ...

Chapter 2.11 by Monnet et al. on #Ammonoids and #Quantitative #Biochronology —A Unitary Association Perspective: rdcu.be/eNedO

Latest further highlight the method based on #coexistences to produce robust ammonoid #biozonations:
doi.org/10.1127/nos/...
doi.org/10.1016/j.pa...
doi.org/10.1016/j.pa...

The early Cenomanian crippsi Event at Lüneburg (Germany): palaeontological and stratigraphical significance of a widespread Late Cretaceous bioevent - Palaeobiodiversity and Palaeoenvironments The early Cenomanian crippsi Event comprises a 1–3-m-thick interval characterised by mass occurrences of the early Cenomanian inoceramid Gnesioceramus crippsi, identified in the uppermost Sharpeiceras...

Chapter 2.10 by Ifrim et al. on #Paleobiogeography of Late #Cretaceous #Ammonoids suggests 4 realms, a recurring Superrealm and loss of provincialism before extinction: rdcu.be/eNebr

Latest underline the importance of #sea-level and #temperature: doi.org/10.1007/s125... doi.org/10.1016/j.ja...

Macroevolution and Paleobiogeography of Jurassic-Cretaceous Ammonoids Jurassic-Cretaceous (J-K) ammonoids experienced remarkably rapid rates of evolution and extinction. The processes that fueled this evolutionary volatility are not well understood. Evolutionary relatio...

Chapter 2.8 by Yacobucci linking #Macroevolution and #Paleobiogeography of #Jurassic-Cretaceous #Ammonoids: rdcu.be/eMHnV inspired a model for speciation: doi.org/10.7208/chic...

Latest show importance of #global and #regional analyses to test models: doi.org/10.1017/pab.... doi.org/10.1038/s414...

Biogeography of Triassic Ammonoids After the end-Permian mass extinction, ammonoids experienced an explosive recovery followed by episodes of radiation and extinction. These events were associated with sudden biogeographic changes ofte...

Chapter 2.7 by Brayard et al. reviewed #Biogeography of #Triassic #Ammonoids: rdcu.be/eMG8P

Latest show cosmopolitanism in Smithian (doi.org/10.1017/pab....) and many #mechanisms shaping distribution depending on interval (doi.org/10.18261/let...; doi.org/10.1016/j.ge...; doi.org/10.1002/spp2...).

In just 3 weeks at La Baume, we logged the Middle #Jurassic succession of subpelagic #marls and #limestones
and collected ~400 #ammonoids and other fossils with Fabrizio Cecca, Jacques Verniers, Myette Guiomar & Lucien Leroy — revealing rich Sonniniidae faunas & a new stratigraphic gap.

Biogeography of Paleozoic Ammonoids The spatial distribution of Paleozoic ammonoids shows an indifferent picture. Time intervals with inconspicuous biogeographic patterns alternate with intervals of well-expressed provincialism. The Dev...

Chapter 2.6 by Korn & De Baets on #Biogeography of #Paleozoic #Ammonoids: rdcu.be/eLCyf

#Fluctuations between widespread #cosmopolitanism and distinct #provincialism with #limited #utility for global #correlation but crucial for regional #zonations:
rdcu.be/eLCBn
dx.doi.org/10.1127/nos/2025/0872

Evolutionary Patterns of Ammonoids: Phenotypic Trends, Convergence, and Parallel Evolution A major goal in evolutionary biology is to characterize and understand the patterns and processes that shape the evolutionary trajectory of clades through time and space. One common pattern in extinct...

Chapter 2.5 by Monnet et al. on Evolutionary Patterns of #Ammonoids: Phenotypic Trends, Convergence, and Parallel #Evolution: rdcu.be/eLwfW

Ongoing study doi.org/10.1017/pab....
doi.org/10.1111/pala...

Spark #theory debate doi.org/10.1111/ede.... dx.doi.org/10.4324/9780...
doi.org/10.1017/9781...

GM in ammonoids virtual models Geometric morphometrics in ammonoids based on virtual modelling

Chapter 2.4 by Monnet et al. on Buckman’s Rules of #Covariation reveal many #ammonoids vary from slender, involute, compressed, smoother to more robust, evolute, depressed, coarser ornamented forms: rdcu.be/eLvTp The generality and causes remain debated: doi.org/10.1016/j.jt...
doi.org/10.26879/1157

Evolution: Morphological complexity fuels rapid species turnover Some animal lineages, such as mammals or trilobites, show particularly high rates of evolution — that is, of species origination and extinction. What makes such lineages special is not clear. A new st...

Chapter 2.3 by Neige & Rouget on #Evolutionary #Trends within #Jurassic #Ammonoids: rdcu.be/eLkNU
focus on shell shape (evolute-involute, depressed-compressed) and size.

Latest link ornament #complexity and rates of evolution but restress #phylogeny: doi.org/10.1016/j.cu...
doi.org/10.1016/j.cu...

Evolutionary Trends of Triassic Ammonoids The Triassic represents a key interval in the evolutionary history of ammonoids. Characterized by the dominance of the Ceratitida with their typical suture line indented on the lobes only, the Triassi...

Chapter 2.2 by Monnet et al. show #Evolutionary #Trends of #Triassic #Ammonoids: rdcu.be/eLkc5 remain poorly understood and a #decoupled #diversity & #disparity

New work reveals PT #extinction selected for smooth, compressed forms (doi.org/10.1130/G487...) & possible size overprint (rdcu.be/eLkrF)

Ancestry, Origin and Early Evolution of Ammonoids In order to put the origin of the Ammonoidea into the broader evolutionary context, we review the hypothesis on the origin of cephalopods in general, the origin of bactritids as well as the origin of ...

Chapter 2.1 by Klug et al. on #Ancestry, #Origin and #Early #Evolution of #Ammonoids: rdcu.be/eLhdZ

Disparity changes more rapid and complex:
doi.org/10.3140/bull... (multiple parallel coiling lineages)
rdcu.be/eLhca (some oldest already coiled)
dx.doi.org/10.4202/app.... (precede #diversity rise)

Parasites of Ammonoids Extant cephalopods are commonly infested by parasites making it plausible that ammonoids also had parasites. We review the fossil evidence of parasitic infestations in ammonoids, which, due to low preservation potential of soft-tissues in ammonoids and parasites, are...

20th chapter by De Baets et al. on #Parasites of #Ammonoids through #paleopathology: rdcu.be/eJqp7

Multiple new reports of parasite-induced #pathologies:
doi.org/10.4202/app....
doi.org/10.18261/let...
doi.org/10.5710/AMGH...

Identifying the culprits remains difficult:
doi.org/10.1007/978-...

15th chapter by Doguzhaeva & Mutvei explored Additional External #Shell Layers Indicative of “Endocochleate Experiments” in Some #Ammonoids: rdcu.be/eJm0q

Covered shell remains poorly explored: doi.org/10.1080/1103...

Support for partial mantle #cover at best: dx.doi.org/10.3140/bull.geosci.1522

The Body Chamber Length Variations and Muscle and Mantle Attachments in Ammonoids The varying body chamber lengths and the different attachment of muscles and mantle to conch wall belong to the major adaptations to their diverse modes of locomotion. Therefore, these traits are indirect indicators of different life styles. The sparse record of...

14th chapter by Doguzhaeva & Mapes on The Body Chamber Length Variations and #Muscle and #Mantle Attachments in #Ammonoids: rdcu.be/eJmJf

Scars suggest powerful retractor muscles (doi.org/10.1093/moll...) but their #function remains debated (doi.org/10.1130/G499...; doi.org/10.1130/G495...)

Report on ammonoid soft tissue remains revealed by computed tomography - Swiss Journal of Palaeontology Findings of ammonoid soft tissues are extremely rare compared to the rich fossil record of ammonoid conchs ranging from the Late Devonian to the Cretaceous/Paleogene boundary. Here, we apply the computed-tomography approach to detect ammonoid soft tissue remains in well-preserved fossils from the Early Cretaceous (early Albian) of NE-Germany of Proleymeriella. The ammonites were found in glauconitic–phosphatic sandstone boulders. Analyses of the high-resolution Ct-data revealed the presence of cameral sheets, the siphuncular tube wall, and the siphuncle itself. The siphuncle is a long, segmented soft tissue that begins at the rear end of the body chamber and comprises blood vessels. Chemical analyses using energy-dispersive spectroscopy (EDS) showed that all preserved soft tissues were phosphatized and are now composed of fluorapatite. The same holds true for preserved shell remains that locally show the nacreous microstructure. We provide a short description of these soft tissue remains and briefly discuss the taphonomic pathway.

13th chapter by Tanabe et al. shows Soft-Part #Anatomy of the #Siphuncle in #Ammonoids: rdcu.be/eJhAM

The structure for #buoyancy regulation is rarely preserved but #ComputedTomography reveals key details: rdcu.be/eJhAB

Also multiple new findings:
doi.org/10.2110/palo...
doi.org/10.2110/palo...

Soft Part Anatomy of Ammonoids: Reconstructing the Animal Based on Exceptionally Preserved Specimens and Actualistic Comparisons

12th chapter by Klug & Lehmann reviews #Soft Part #Anatomy of #Ammonoids: rdcu.be/eJgOJ

New studies underline that rare #exceptionally #preserved specimens (doi.org/10.1130/G495...; rdcu.be/eJgSe) as well as actualistic comparisons (rdcu.be/eJgHQ) to reconstructing these animals.

Ammonoid Color Patterns Color patterns on ammonoid cephalopods are rarely preserved despite the fact that millions of the shells of these extinct animals have been recovered from Devonian through the Upper Cretaceous rocks that were deposited in a wide variety of marine environments around...

2nd chapter by Mapes & Larson dealt with “ #Ammonoid #Color #Patterns”: doi.org/10.1007/978-...

In the meantime, additional fake and true color patterns have been found in #ammonoids (doi.org/10.1111/brv....) and #nautiloids (doi.org/10.54103/203...).

🚨New paper🚨

A new work led by Román Ramírez-Muñoz on the Early #Carboniferous ammonoid biostratigraphy from the Riotinto-Nerva Mining Basin, #Huelva province, SW Spain.

Fresh Palaeozoic #ammonoids 🦑

www.schweizerbart.de/papers/njgpa...

A vibrant digital drawing of an ammonite.

Ammonium
#drawing #art #animal #comic #cartoon #vibrant #digitalart #digitaldrawing #sea #ocean #ammonoidea #ammonoids #ammonite #marine #marinelife #shell

Evolution: Morphological complexity fuels rapid species turnover: authors.elsevier.com/a/1kH973QW8S... #paleontology #paleobiology #evolution #fossils #ammonoids