The Additional External Shell Layers Indicative of “Endocochleate Experiments” in Some Ammonoids

Doguzhaeva, Larisa A.; Mutvei, Harry

doi:10.1007/978-94-017-9630-9_15

Cited by 8 publications

(10 citation statements)

References 15 publications

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“…On internal moulds, the attachment marks can occur as small tubercles, shallow depressions or spots. These show often dark brownish or reddish colors due to pyrite or manganese hydroxides (Jordan 1968;Richter 2002;Richter and Fisher 2002;Doguzhaeva and Mutvei 2015). These differences corroborate that the inside of the body chamber wall originally carried attachment marks, which were either shallow pits, elevations or spots rich in organic material.…”

Section: Fossilization Of Mantle and Muscle Attachment Marksmentioning

confidence: 77%

“…14.1, 14.2, 14.3, 14.4;Doguzhaeva 2014), Ancyloceras (Doguzhaeva and Mikhailova 1991), Ptychoceras (Doguzhaeva and Mutvei 2015), Pseudocrioceratites (DLA, personal observation), and possibly in Baculites (Kennedy et al 2002, pl. 6, Figs.…”

Section: Umbilical Large Tongue-like Marksmentioning

confidence: 94%

“…The hypothesis of the soft body size exceeding the body chamber volume arose from the additional external shell wall layers in some taxa, which caused or required a mantle extension over the external shell surface for the extra shell secretion; this was proposed by Drushchits et al (1978) and supported by Doguzhaeva and Mutvei (1989, 1991, 1996, 2015. This hypothesis received further support from the discovery of the thin fragile apertural margin in Ptychoceras (Doguzhaeva and Mutvei 1993) and parabolic structures on the external surface of the body chamber in Indosphinctes (Doguzhaeva 2012).…”

Section: Morphological Indications Of Jet-powered Swimming In Ammonoidsmentioning

confidence: 96%

“…The canals are thought to have housed the mantle extensions and served for the body and body chamber attachment (Doguzhaeva and Mutvei 2015). In ammonoids, the mantle was probably attached along its apertural edge to the shell aperture in a manner similar to that of Nautilus.…”

Section: Pore Canals and Assumed Porous Apertural Bandmentioning

confidence: 99%

“…14.2). In Ptychoceras, the small rounded marks within the tongue-like umbilical marks are arranged in two pairs, one of which is situated in front of the last septum, and the next pair is situated near the midpoint of the body chamber (Doguzhaeva and Mutvei 2015).…”

Section: Umbilical Large Tongue-like Marksmentioning

confidence: 99%

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The Body Chamber Length Variations and Muscle and Mantle Attachments in Ammonoids

Doguzhaeva

Mapes

2015

Topics in Geobiology

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Section: Fossilization Of Mantle and Muscle Attachment Marksmentioning

confidence: 77%

Section: Umbilical Large Tongue-like Marksmentioning

confidence: 94%

Section: Morphological Indications Of Jet-powered Swimming In Ammonoidsmentioning

confidence: 96%

Section: Pore Canals and Assumed Porous Apertural Bandmentioning

confidence: 99%

Section: Umbilical Large Tongue-like Marksmentioning

confidence: 99%

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The Body Chamber Length Variations and Muscle and Mantle Attachments in Ammonoids

Doguzhaeva

Mapes

2015

Topics in Geobiology

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An Ordovician nectocaridid hints at an endocochleate origin of Cephalopoda

Smith

2019

J. Paleontol.

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Nectocaridids are soft-bodied Cambrian organisms that have been controversially interpreted as primitive cephalopods, at odds with the long-held belief that these mollusks evolved from a shell-bearing ancestor. Here, I document a new nectocaridid from the Whetstone Gulf Formation, extending the group's range into the Late Ordovician. Nectocotis rusmithi n. gen. n. sp. possesses a robust internal element that resembles a non-mineralized phragmocone or gladius. Nectocaridids can be accommodated in the cephalopod total group if the earliest cephalopods (1) inherited a non-mineralized shell field from the ancestral mollusk; and (2) internalized this shell field. This evolutionary scenario would overturn the traditional ectocochleate, Nautilus-like reconstruction of the ancestral cephalopod, and indicate a trend towards increased metabolic efficiency through the course of Cambrian–Ordovician evolution.UUID: http://zoobank.org/ed594200-37b9-4642-bd8f-4fb72dc544eb

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Spatial distribution of oncocerid cephalopods on a Middle Devonian bedding plane suggests semelparous life cycle

Pohle

Fuchs

Korn

et al. 2020

Sci Rep

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Reproductive strategies of extinct organisms can only be recognised indirectly and hence, they are exceedingly rarely reported and tend to be speculative. Here, we present a mass-occurrence with common preservation of pairs of late Givetian (Middle Devonian) oncocerid cephalopods from Hamar Laghdad in the Tafilalt (eastern Anti-Atlas, Morocco). We analysed their spatial occurrences with spatial point pattern analysis techniques and Monte carlo simulations; our results shows that the pairwise clustering is significant, while ammonoids on the same bedding plane reveal a more random distribution. it is possible that processes such as catastrophic mass mortality or post-mortem transport could have produced the pattern. However, we suggest that it is more likely that the oncocerids were semelparous and died shortly after mating. These findings shed new light on the variation and evolution of reproductive strategies in fossil cephalopods and emphasise that they cannot be based on comparisons with extant taxa without question.Among the two major clades of living cephalopods, the Coleoidea and Nautiloidea, there is a broad range of reproductive strategies. Coleoids were long considered to be invariably semelparous (reproducing only once), while Nautilus is iteroparous (giving rise to offspring multiple times) 1 . However, in recent years, squid, octopus and cuttlefish were shown to exhibit a wide range of reproductive strategies and life cycles 2 . Nevertheless, although its reproductive biology is still poorly known, Nautilus is unique among living cephalopods in its polycyclic spawning and long life span, in contrast to the monocyclic spawning (which can occur in separate batches or during an extended time period) of the relatively short-lived coleoids 1,2 .Studies of the reproduction strategies of the mostly externally shelled fossil cephalopods are very rare, largely because the scarcity of soft part preservation strongly limits the possibilities of these investigations. Yet, cephalopods such as ammonoids, bactritids and orthocerids possess small protoconchs and thus eggs and hatchlings; accordingly, they are often considered to be close to coleoids in their reproductive strategy, while cephalopods with large embryonic shells are generally considered to be closer to the living Nautilus 3-6 . In addition, nautiloids are usually thought to be K-strategists (type I survivorship), while coleoids, ammonoids, bactritids and partly orthocerids are seen as r-strategists (type III survivorship 3,7 ). However, since both K-and r-strategies occur among recent coleoids combined with a semelparous life cycle 2 , these assumptions may be too simple. In addition, the paradigm of K-and r-strategy 8 has been abandoned in the field of life-history evolution for some time 9 .Previous studies have focused on life history traits that can be assessed with some reliability. For example, the mode of life of hatchlings can be inferred from the size of the embryonic shell and facies distribution, while the relative size of the hatchling to th...

show abstract

The Additional External Shell Layers Indicative of “Endocochleate Experiments” in Some Ammonoids

Cited by 8 publications

References 15 publications

The Body Chamber Length Variations and Muscle and Mantle Attachments in Ammonoids

The Body Chamber Length Variations and Muscle and Mantle Attachments in Ammonoids

An Ordovician nectocaridid hints at an endocochleate origin of Cephalopoda

Spatial distribution of oncocerid cephalopods on a Middle Devonian bedding plane suggests semelparous life cycle

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