73552678
A New Type of Shell Malformation Caused by Epizoans in Late Jurassic Ammonites from Central Russia
A new type of shell damage on Late Jurassic ammonite Kachpurites fulgens is described. The new type of shell malformation consists of small elongated pits, arranged in groups on the surface of ammonite shell and concentrated near the terminal aperture. The examination of the pits demonstrated no signs of drilling, biting, or healing of punctures. The shell layers in the pits are bent downward without changing in thickness. At the same time the pits, in some cases, significantly distort the shape of the shell walls. Deformed growth lines are associated with some of the pits. All of this supports the hypothesis that the pits had been formed by epifauna located at a flexible uncalcified part of the periostracum in the apertural region of the growing ammonite shell. It is likely that epizoan attachment led to the deformation of the thin periostracum film and to the distortion of the growing shell wall. The nature of epizoans is discussed, but remains unclear due to their rather poor preservation. The relationship between epizoans and ammonites is also an open question: they could have been parasites, but other types of biotic relationships cannot be entirely ruled out.
128494070
Limpet home depressions in Cretaceous ammonites
Remarkable large pits were found on the shell surface of many ammonites from the Turonian-Maastrichtian sediments of Hokkaido, northern Japan, and Sakhalin, Russia. These pits are (1) round to elliptical in shape; (2) up to 20 mm (usually around 10 mm) in diameter; (3) shallow depressions to deep holes that almost penetrate the shell: (4) occasionally healed by a thin shell blister from inside the shell; (5) often overlapping one another; (6) several to more than 170 in number on one flank of the ammonites; (7) found on both flanks and predominantly on the body chamber and the final volution of the phragmocone; and (8) found only in the two families Pachydiscidae and Puzosiidae, predominantly of more than 300 mm in shell diameter. They can best be interpreted as the home depressions of patellogastropod limpets. The presence of pits on both flanks of the ammonites and those healed from inside the shell strongly suggest that the limpets were dwelling on mature swimming ammonites. Host specifity, their very small shell size compared with the host ammonites, and sparse Occurrence in sediments favor a mode of life as obligate pseudoplankton. We suggest that this remarkable limpet-ammonite association was well established in northwestern Pacific bioprovinces during the late Cretaceous. Taking this live association and the depth limit of algal growth as food for the limpets into consideration, the mature ammonites dwelled or periodically visited the upper layer of the euphotic zone, probably less than around 20 m in depth. ***Ammonite, limpet, home depression, life mode, pseudoplankton, Cretaceous.
129505459
Alleged mosasaur bite marks on Late Cretaceous ammonites are limpet (patellogastropod) home scars
New data contradict the mosasaur-bite hypothesis for the origin of holes seen in Placenticeras ammonites from the Late Cretaceous Pierre Shale and Bearpaw Formation of the western interior of North America. Observations of a limpet-infested Placenticeras ammonite and of several Placenticeras specimens with radular scratch marks reveal that the limpets dwelled on floating ammonites, and their homing activity produced circular depressions. When altered during diagenesis, the depressions mimic tooth punctures. Crushing experiments on fresh Nautilus shells using a mosasaur robot show that mosasaur bites could not have produced holes resembling those in the fossils. Furthermore, sectioning of “bitten” ammonites reveals that sepia are sometimes intact under the holes, an observation irreconcilable with penetration by a tooth. We present an alternative interpretation that the alleged “bite marks” in Placenticeras ammonites are really limpet home scars that were altered after burial. While predation of mosasaurs on ammonites remains a possibility, it would have to be demonstrated by other criteria. Our findings do not support mosasaur-ammonoid coevolution in the Late Cretaceous.
128848079
Epizoic Stramentid Cirripedes on Ammonites from Late Cretaceous Platy Limestones in Mexico
Abstract The discovery of platy limestone deposits in northeastern Mexico has led to the collection of well-preserved stramentids of early Turonian age from Vallecillo, state of Nuevo León, and of early Coniacian age from El Carranza, state of Coahuila. Stramentum (Stramentum) pulchellum (Sowerby, 1843) colonized the ammonite shells during the lifetime of the animals, occasionally in two subsequent generations. Colonization of the ammonite shell by Stramentum (S.) pulchellum was hindered by strong ornamentation only. The ammonites did not interfere with their epizoans. Colonization during lifetime shows that these ammonites dwelled in well-oxygenated water levels near the surface, and most stramentids were embedded alive. The known paleobiogeographic occurrence of Stramentum (S.) pulchellum and its long stratigraphic occurrence are considerably enlarged by our findings. The pseudoplanktonic mode of life of Stramentum, and attachment to ammonite shells, may have been a response of a once benthic organism to repeated oxygen-deficient conditions on the seafloor of mid-Cretaceous oceans, i.e., to oceanic anoxic events (OAEs).
86427320
Abnormalities as natural experiments: a morphogenetic model for coiling regulation in planispiral ammonites
Abstract Exceptional examples of planispiral ammonites that were infested by epizoans during life display alterations of their normal coiling. Most commonly, the epizoan(s) settled on the venter of the ammonite and constituted an obstacle for the whorl tube grown one whorl later; this caused lateral deviation of the whorl tube and tilting of the ammonoid because of changes in the hydrostatic condition; from here on, the whorl tube periodically crossed the venter of the preceding whorl, thereby producing a zigzag coiling pattern. Some epizoans, which were particularly centered on the midventer, provoked detachment between whorls. In a few cases, lateral placement of the epizoan did not directly obstruct the normal growth path of the ammonite but induced a trochospiral coiling pattern. Both the zigzag and the trochospiral pattern were created when the ammonite tried to maintain the growth direction within the vertical plane at the same time as whorls remained in contact along a differentiated dorsal epithelium. The aperture reacted to changes in growth direction, to maintain also a permanent angle with the vertical direction. Growth direction, then, was a major morphogenetic parameter in ammonites, because it contained the necessary instructions for correct shell coiling. The model based on the observation of fabricational defects has been tested by a theoretical model by which the different situations so far observed are simulated and in which the parameters are the morphogenetic instructions inferred to have been present in the biological system.
96454605
Devonian Pearls and Ammonoid-Endoparasite Co-Evolution
Raised shell projections on the inner shell walls that form pits on the internal moulds of Devonian ammonoids have been known for several decades. New specimens from Morocco reveal novel details of these structures; most, if not all, of which consist of a capsule of ammonoid shell that covers tiny tubes attached to the outer (= lateral or ventral) shell wall from the inside. In accordance with comparable Recent occurrences of similar structures in molluscs, we use the term “pearls” for these structures and the pits they form on the internal moulds. The nature of these encapsulated tubes is described and discussed. Because of the presence of these tubes inside the pearls, pearl arrangement, and their similarity to Recent mollusc occurrences, the tubes are interpreted as traces of parasitoses. The pearls and pits were grouped into five types based on differences in morphology, size, and arrangement. Then, having used these traits to perform a simple cladistic analysis, the resulting cladogram was compared to the phylogeny of ammonoids. Based on this comparison, it appears likely that the parasites underwent a co-evolution with the ammonoids, which lasted 10 to 15 Ma. Patterns of evolutionary events include co-speciation, “drowning on arrival” (end of parasite lineage near base of a new host clade), and “missing the boat” (parasite lineage does not adapt to a new host clade, thus not evolving a new parasite clade). Because of the lack of fossilised soft tissue, only speculations can be made about the systematic affiliation of the parasites, their life-cycle, infection strategy, and ecological framework. Some co-occurring bivalves also have pits reminiscent to structures caused by trematodes in Recent forms. Based on the available information, the tubes are interpreted as artefacts of trematode infestations, which, if correct, would extend the fossil record of parasitic trematodes into the Early Devonian.
55240203
The Soft-Tissue Attachment Scars in Late Jurassic Ammonites from Central Russia
Soft-tissue attachment scars of two genera and four species of Late Jurassic craspeditid ammonites from the Russian Platform are described. A previously suggested relationship between lateral attachment scars and ammonoid hyponome is confirmed, however, a new interpretation is proposed for dorsal attachment scars: they could have been areas not only for attachment of the dorsal (nuchal) retractors, but also of the cephalic retractors. The new type of the soft-tissue attachment—anterior lateral sinuses, located between the lateral attachment scars and the aperture of the ammonite body chamber is described. Enclosed elliptical or subtriangular areas in apertural parts of the anterior lateral sinuses were found for the first time. Their presence and location suggest that this structure could have been used for attaching the funnel-locking apparatus, similar to those of coleoids. A transformation of shape and position of lateral attachment scars through the evolution of the Late Jurassic craspeditid lineage starting from platycones (Kachpurites fulgens) to keeled oxycones (Garniericeras catenulatum) is recognized.
129908262
Boreal-tethyan correlation of the Jurassic-Cretaceous boundary interval by magneto- and biostratigraphy
As a result of detail sampling and paleomagnetic study of the 27-m-thick section of Jurassic-Cretaceous boundary beds in the Nordvik Peninsula (Anabar Bay, Laptev Sea), a succession of M-zones correlative with chrons M20n-M17r is established for the first time in the Boreal deposits. Inside the normal polarity zone corresponding to Chron M20n, a thin interval of reversed polarity, presumably an equivalent of the Kysuca Subzone (M20n.1r), is discovered. The other thin interval of reversed polarity established within the next normal polarity zone (M19n) is correlated with the Brodno Subzone (M19n.1r). The same succession of normal and reversed polarity zones has been discovered recently in the Jurassic-Cretaceous boundary beds of the Tethyan sections: in the Bosso Valley (Italy), at the Brodno (Slovak Republic) and Puerto Escaño (Spain) sites. Correlation of successions established lead us to conclusion, that the Jurassic-Cretaceous boundary corresponds in the Panboreal Superrealm to a level within the Craspedites taimyrensis Zone of the upper Volgian Substage. Hence, the greatest part of Volgian Stage should be included into the Jurassic System. Biostratigraphic data do not contradict this conclusion.
73660803
Infrazonal Subdivision of the Volgian Stage in its Type Area Using Ammonites and Correlation of the Volgian and Tithonian Stages
The Volgian Stage of the Russian Platform is subdivided into 3 substages and 9 zones, within which 37 biohorizons are recognized. Only the lower Volgian is characterized by occurrences of ammonites of Sub-Mediterranean origin, which permits direct correlation to be made with the Tithonian Stage. Rare records of Haploceras in the basal middle Volgian are not able to be used for correlation, and the overlying part of the Volgian stage lacks any Sub-Mediterranean or Mediterranean faunal elements in the ammonite faunas. Recent advances in magnetostratigraphic studies of the upper part of the Volgian Stage in northern Siberia lead to a correlation of the uppermost middle and upper Volgian of this area with the Tithonian succession. These results can also be effectively used for correlating the Volgian ammonite zones of the Russian Platform with those of the Tithonian Stage.
84426175
Late Volgian Kachpurites Spath (Craspeditidae, Ammonoidea) of the Russian platform
Ammonites of the genus Kachpurites are characteristic of the lower part of the Upper Volgian Substage of the Russian Platform. K. fulgens fulgens (Trautschold), K. fulgens tscheremkhensis Mitta et al., K. subfulgens (Nikitin) are established in the fulgens zone. The genus Kachpurites also includes ammonites previously described as Anivanovia mola Kiselev. The holotype of Volgidiscus singularis Kiselev belongs to K. mola, wheras some of its paratypes belong to Craspedites krylovi Prigorovsky. The generic name Anivanovia Kiselev, 2003 is considered as a junior subjective synonym Kachpurites Spath, 1924. The beds with Kachpurites mola are in the basal part of the Upper Volgian subditus Zone. Species of the genus Kachpurites are described, and macro- and microconchs are established within the species.
84903239
Discovery of the jaw apparatus of the upper Volgian Ammonite Kachpurites fulgens (Craspeditidae)
The jaw apparatus of the genus Kachpurites (Ammonoidea, Craspeditidae), consisting of a pair of aptychi and a beak-shaped upper jaw is described and figured for the first time. A new aptychus species Praestriaptychus fulgens sp. nov. is established. Aptychi of this species are elongated-triangular, weakly ribbed, with a well-developed inner organic layer and a considerably thinner, often poorly preserved external calcite layer. Specimens of the type series were found in the body chamber of ammonites Kachpurites fulgens (Trautschold), from the Upper Jurassic (Upper Volgian) Kachpurites fulgens Zone of Moscow and the Moscow Region.
140188011
Sublethal punctures in body chambers of Mesozoic ammonites (forma aegrafenestra n. f.), a tool to interpret synecological relationships, particularly predator-prey interactions
The new forma aegrafenestra n. f. sensuHölder (1956) is introduced to describe healed injuries to the body Chambers of Jurassic/Cretaceous ammonites, primarily behind the peristome but normally excluding the peristome itself. The different outlines and positions of these window-like sublethal injuries indicate two different Subtypes of injury inflicted by two different types of predator. Some of the large-scale ventral injuries occurring since the Late Devonian were presumably due to attacks by durophagous vertebrates, whereas the smaller, more or less rounded and mainly lateral puncture marks in Liassic to Cretaceous ammonite Shells can be traced back to unsuccessful attacks by stomatopod crustaceans. Identification of the specific predators responsible for characteristic injuries will give information about synecological relationships and life-modes of the attacked ammonites.KurzfassungRegenerierte Wohnkammerverletzungen an mesozoischen Ammonitengehäusen, die nicht von der interimistischen Gehäusemündung ausgehen, sondern in einem diskreten Abstand hinter ihr angelegt wurden, werden in der TraditionHölder’s (1956) als forma aegrafenestra n. f. beschrieben. Die Ursache der Verletzungen wird in Abhängigkeit von ihrer Konfiguration und der Position am Gehäuse auf zwei unterschiedliche Gruppen von Prädatoren zurückgeführt. Während die meist großflächigen, ventralen Verletzungen, die seit dem Paläozoikum auftreten, eher auf Attacken durophager Fische hinweisen, scheinen die seit dem Unter-Jura bekannten, kleineren Schalenausbrüche überwiegend auf einer Gehäuseflanke auf erfolglose Angriffe von Stomatopoden (Crustacea) zurückzugehen. Die Rückführung der charakteristischen Prädationsspuren auf jeweils konkrete Verursacher gibt Aufschluss über die mutmaßlichen Lebensweisen der betroffenen Ammonoideen.
17896258
Syn-Vivo Bioerosion of Nautilus by Endo- and Epilithic Foraminiferans (New Caledonia and Vanuatu)
A variety of syn-vivo bioerosion traces produced by foraminiferans is recorded in shells of Nautilus sampled near New Caledonia and Vanuatu. These are two types of attachment scars of epilithic foraminiferans and two forms of previously undescribed microborings, a spiral-shaped and a dendritic one, both most likely being the work of endolithic 'naked' foraminiferans. Scanning electron microscopy of epoxy-resin casts of the latter revealed that these traces occur in clusters of up to many dozen individuals and potentially are substrate-specific. The foraminiferan traces are the sole signs of bioerosion in the studied Nautilus conchs, and neither traces of phototrophic nor other chemotrophic microendoliths were found. While the complete absence of photoautotrophic endoliths would be in good accordance with the life habit of Nautilus, which resides in aphotic deep marine environments and seeks shallower waters in the photic zone for feeding only during night-time, the absence of any microbial bioerosion may also be explained by an effective defence provided by the nautilid periostracum. Following this line of reasoning, the recorded foraminiferan bioerosion traces in turn would identify their trace makers as being specialized in their ability to penetrate the periostracum barrier and to bioerode the shell of modern Nautilus.
82279049
Predation on Nautilus
Little has been written regarding predation on Nautilus, because information on the subject has largely been limited to inferences based on indirect evidence, such as healed injuries, shell breaks, and borings. For example, Willey (1902) remarked on the presence of healed severe injuries to the hoods of several males and speculated that they might be due either to attacks by fishes or to fighting between sexes. Haven (1972) regarded shell breakage and hood injuries in N. pompilius as a fairly common product of fighting within the species and demonstrated that the distinctive, V-shaped breaks so common in Nautilus shells are a product of biting (Haven, 1972, Figs. 4 and 5). Arnold (1985) described and categorized a wide variety of shell abnormalities in N. pompilius from the same region. In addition, evidence indicates that Nautilus is regularly preyed upon by Octopus, and attacks on Nautilus by fishes have now been documented. This chapter briefly summarizes the results of previous studies and presents new information regarding predation on Nautilus.
20703803
The morpho-mechanical basis of ammonite form.
Ammonites are a group of extinct cephalopods that garner tremendous interest over a range of scientific fields and have been a paradigm for biochronology, palaeobiology, and evolutionary theories. Their defining feature is the spiral geometry and ribbing pattern through which palaeontologists infer phylogenetic relationships and evolutionary trends. Here, we develop a morpho-mechanical model for ammonite morphogenesis. While a wealth of observations have been compiled on ammonite form, and several functional interpretations may be found, this study presents the first quantitative model to explain rib formation. Our approach, based on fundamental principles of growth and mechanics, gives a natural explanation for the morphogenesis and diversity of ribs, uncovers intrinsic laws linking ribbing and shell geometry, and provides new opportunities to interpret ammonites' and other mollusks' evolution.
126789076
Dorsal shell wall in ammonoids
In ammonoids, a soft body organ (possibly a supracephalic mantle fold), extending from the conch aperture secreted aragonitic wrinkles, forming a layer on the surface of the preceding whorl. The dorsal shell wall consists of the outer and inner components which were deposited sequentially, beginning at the aperture of the living chamber inwards. The dorsal wall attains its full thickness near the last septum. The outer component is visible in the apertural region and is smooth or wrinkled; it is called the wrinkled layer in the latter case. The wrinkles may be continuous, interrupted, or form isolated patches arranged in rows. The wrinkles are usually triangular in cross section. A further stage of dorsal wall development involves filling in the space between the apices of triangles, and then adding one or more inner prismatic layers from the inside of the living chamber. This pattern occurs at least in the postembryonic stage of all genera studied, belonging to five suborders of Ammonoidea ranging from Late Carboniferous to Late Cretaceous. In many genera, the outer component of the dorsal shell wall exhibits remarkable ontogenetic change in its ultrastructure and micro-ornament. It may be compared with the black film of Recent Nautilus shells with respect to place of formation. The outer component of the ammonoid dorsal shell wall is regarded as a product of organic secretion and carbonate precipitation in the area of the supracephalic mantle fold.
87319305
Allonautilus; a new genus of living nautiloid cephalopod and its bearing on phylogeny of the Nautilida
Living ectocochliate cephalopods have long been thought to be restricted to a single genus, Nautilus Linnaeus, 1758, comprising five or six extant species. The shells of two species, N. scrobiculatus Lightfoot, 1786, and N. perforatus Conrad, 1847, are quite distinct, but no soft-parts were known until 1984, when N. scrobiculatus was seen alive for the first time. Dissections show that significant anatomical differences exist between N. scrobiculatus and other Nautilus species, including differences in gill morphology and details of the male reproductive system. These differences, along with phylogenetic analysis of extant and selected fossil nautiloid species, indicate that N. scrobiculatus, and N. perforatus should be distinguished from Nautilus as a newly defined genus, Allonautilus. This analysis contradicts previous phylogenies proposed for the Nautilida, which placed Nautilus as the last-evolved member of the order. We surmise that Allonautilus is a descendent of Nautilus, that the latter is paraphyletic, and first evolved in the Mesozoic, rather than in the late Cenozoic, as has been previously suggested.
133786513
Mode of life and habitat of scaphitid ammonites
Abstract Scaphitid ammonites (scaphites) are among the most common ammonites in the Upper Cretaceous of the U.S. Western Interior. We have examined species of Hoploscaphites from the Campanian and Maastrichtian Pierre Shale and Bearpaw Shale for clues about their mode of life and habitat. Like most other ammonites, scaphites exhibit determinate growth. The “morphogenetic countdown” begins at the point at which the shell departs from the spiral coil and develops into a shaft and recurved hook. This is accompanied by a reduction in the spacing of ribs and tubercles on the hook and the formation of a constriction and varix at the aperture. Internally, this coincides with a decrease in septal spacing. The common association of scaphites and benthic fossils (e.g., Inoceramus) is interpreted as reflecting oxygen-rich episodes in the history of the Western Interior Seaway. Habitat depths are estimated at less than 100 m, based on faunal associations and studies of the mechanical strength of the septa and siphuncle. Analyses of the isotopic composition of the shells suggest that the animals lived near the sea floor. The high angle of orientation of the aperture at maturity (approximately 100°) seems incompatible with a nektobenthic mode of life. The constricted aperture ending in a thin lip may also have restricted unimpeded movement of long, muscular arms protruding from the aperture. Adults were probably poor swimmers, based on a comparison of their musculature (as inferred from their muscle scars) with that of nautilus (assuming that such a comparison is valid). The lack of a hyponomic sinus on the midventer would have prevented the animal from extending its hyponome below the shell in order to swim forward. As a consequence, scaphites may have been limited in their movement to swimming backward or downward, and may have exploited a low-energy lifestyle, remaining at a single site for an extended period of time. They may have consumed small prey in the water column, which is consistent with the presence of an aptychus-type lower jaw.
56340634
Khetoceras (Craspeditidae, ammonoidea)—A new genus from the Volgian stage of northern Middle Siberia, and parallel evolution of Late Volgian boreal ammonites
A new ammonite genus, Khetoceras (Craspeditinae), is proposed, showing an atypical combination of features for the subfamily (arrowlike cross-section and prominent constrictions). A new subfamily Subcraspeditinae is proposed within the family Craspeditidae. An increase in whorl overlap was the major trend in the evolution of the Late Volgian subfamilies belonging to Craspeditidae (Craspeditinae, Garniericeratinae, and Subcraspeditinae) leading to the appearance of discoid morphotypes with a narrow (or acute) cross-section in all these subfamilies. However, while this evolutionary trend dominated the evolution of Garniericeratinae and less so Subcraspeditinae, it was not so prominent in the Volgian Craspeditinae, in which this morphotype only developed in northern Siberia (genus Khetoceras), where at that time the other two subfamilies were absent.
205306306
Crustaceans from bitumen clast in Carboniferous glacial diamictite extend fossil record of copepods.
Copepod crustaceans are extremely abundant but, because of their small size and fragility, they fossilize poorly. Their fossil record consists of one Cretaceous (c. 115 Ma) parasite and a few Miocene (c. 14 Ma) fossils. In this paper, we describe abundant crustacean fragments, including copepods, from a single bitumen clast in a glacial diamictite of late Carboniferous age (c. 303 Ma) from eastern Oman. Geochemistry identifies the source of the bitumen as an oilfield some 100-300 km to the southwest, which is consistent with an ice flow direction from glacial striae. The bitumen likely originated as an oil seep into a subglacial lake. This find extends the fossil record of copepods by some 188 Ma, and of free-living forms by 289 Ma. The copepods include evidence of the extant family Canthocamptidae, believed to have colonized fresh water in Pangaea during Carboniferous times.
44843085
Fossil Parasitic Copepods from a Lower Cretaceous Fish
Well-preserved Lower Cretaceous fossil copepods related to the super-family Dichelesthioidea have been collected from the gill chamber of the ichthyodectid fish Cladocyclus gardneri. The fossils provide conclusive evidence suporting recent theories that link caligid copepods, which are parasitic on fish, to the invertebrate-associated siphonostomes. This is the first discovery of fossil parasitic copepods, and they are by far the oldest copepods of any sort known.
87475359
Kabatarina pattersoni; a fossil parasitic copepod (Dichelesthiidae) from a Lower Cretaceous fish
Thirteen fragments of a fossil parasitic copepod have been recovered from two specimens of the fossil teleost fish, Cladocyclus gardneri, from the Santana Formation in Brazil. The fossil fragments are preserved in the round and represent both sexes of a primitive species of the family Dichelesthiidae, related to the modem genera Anthosoma and Dichelesthium.