No more nautiloids?

First of all, there is growing evidence that „nautiloids“, like the good old „pisces“ is a term that is obsolete for taxonomy because it is in use for a paraphyletic group. Remember that „fish“ is term for aquatic animals with a gill with a certain fish-like appearance. It is negative exclusive, because tetrapods like mice or man, which are a clade of the Ostheichtyes (bony fish) are not fish.
Nautiloids are classically considered as „primitive“ cephalopods with an outer shell. In contrast, coleoids are the group of internally shelled cephalopods that dominate modern group diversity (see here). The term „nautiloid“ was used by paleontologist for non-ammonoid externally shelled cephalopods with the exclusion of bactritoids and, sometimes, also of orthocerids (this is more or less synonymous with the concept „palcephalopoda“).
This concept was based on the classical hypothesis that Nautilus is a descendent of a group of Paleozoic cephalopods that are called „Oncocerida“.This hypothesis was questioned several times [e.g. Dzik, 1984; Korn & Dzik, 1992], but nobody worked on this problem ever since.
Recent molecular divergence dates additionally and independently are in contrast to the classical oncocerid-origin hypotheses [see here]. These divergence estimates point toward a quite late divergence of nautilus/coleoids (416 Ma, latest Silurian). Because coleoids verifiable are late descendents from orthocerids and orthocerids and oncocerids split already by the early Ordovician it appears reasonable to argue that Nautilus is an indirect descendent of orthocerids (we did this here).
As a consequence the classical use of the term „nautiloids“ would, like in „fishes“, be a paraphyletic clade that excludes coleoids. (see our figure below). This is a little bit a dilemma, because: How to name the various paleozoic stem group cephalopods?
Our new paper makes it obvious that it needs some effort to puzzle out the origin of the Nautilida (the group of Nautilus).

Nectocaris is not a cephalopod

In may 2010 a paper came out that spectacularly claimed that primitive coleoid-like cephalopds existed already during the Cambrian. The authors interpreted the fossil Nectocaris as a shell-less cephalopod. In two recent [Mazurek & Zaton, 2011; Kröger et al. 2011] papers convincing arguments were found that this interpretation is wrong. See also discussions here, here, and here.

Hyoliths are not cephalopod ancestors

Another exotic hypothesis on the origin of cephalopods is the idea that swimming cone shape Cambrian organisms (Hyoliths) were its ancestors. I call this the planktonic-origin hypothesis. It was expressed repeatedly by Dzik [ eg. 1981, 2010] and appears as an interesting alternative to the more widely accepted hypotheses that cephalopods originated from benthic monoplacopohoran like mollusks [see our review here and this discussion].
Recently Ed Landing and me submitted a paper that finds arguments against the planktic-origin hypothesis. These are our arguments:
Cardinal processes, conch microstructure, protoconch, and small apical angle
distinguish hyoliths from the oldest cephalopods. No evidence for an evolutionary transition between hyoliths and early cephalopods exist.
Dzik‘s hypothesis is based on the idea that primitive cephalopods had small spherical initial shells and that the earliest cephalopods had planktic/plankton feeding hatchlings. In our paper we compile evidence that early cephalopods had no such planktotroph hatchlings. Instead the earliest spherical, small initial chambers which are indicative of planktotrophy of hatchlings are known from early Ordovician orthocerids.

What are “nautiloids”?

This question is easily answered by neontologists: Nautiloidea (subclass) are the others beneath the soft bodied cephalopods, the Coleoidea (subclass). Of the several hundred known living cephalopod genera [Felley et al. 2003, 1], only two are nautiloids, Nautilus, and Allonautilus. For neontologists, nautiloids are the few cephalopods which have primarily an outer shell [Lindgren et al. 2004, 2].
More problems arise for the classification of fossil cephalopods. Because nautiloids, are simply considered as stem-group cephalopods, nautiloids in the broad, classical sense are thus all old cephalopods that are not coleoids or ammonoids (this is the practice of the Treatise). However, the evolutionary history that lies between the appearance of the first cephalopod and between the appearance of the first coleoids is long and complex, thousands of extinct genera are known. Here, the neontological bipartition of cephalopods into nautiloids, and coleoids causes a great dilemma for the classification of fossil cephalopods, because it does not allow for the erection of new total groups that would express phylogenetic hypotheses, above the subclass level fixed by the Coleoidea.
There are only few exceptions. Some extinct large monophyletic offshoots (plesions) can be excluded and treated as additional subclasses (e.g. ammonoids). However, for several proposed subclasses, such as actinoceroids, and bactritoids it is not clear if they represent paraphyletic/grade groups, or even polyphyletic groups [Kröger and Mapes, 2007a, b ]. For others, such as the Orthoceratoidea it would be appropriate to include new higher taxa above the subclass and below the class level, in order to classify extinct cephalopods in total groups that are transitional between coleoids and Nautilus.
One approach to do this is that of Lehmann and Hillmer (1980), which distinguish between the Palcephalopoda and Neocephalopoda. The Neocephalopoda contain the ammonoids, coleoids and the diverse cephalopods with straight and coiled shells that are classified within the “Orthoceroidea”, and “Bactritoidea”, and the Lituitida. The Palcephalopoda are the remaining stem-group cephalopods.
When accepting the bipartition of cephalopods into Neocephalopods and a stem-group grade than, the Palcephalopoda would  be a subjective junior synonym of the Nautiloidea. In fact, this is the implicit usage of the term “nautiloid” that I use since a few years in my own papers and that also has been practiced by the e.g. Manda and Turek (2009): nautiloids are stem group cephalopods exclusive ammonoids, bactritoids, coleoids and orthoceroids. Here I will call them “nautiloids sensu stricto”. In contrast the classical nautiloids of the Treatise, and that of the neontologist are all non-ammonoid cephalopods with an external shell. Here I will call them “nautiloids sensu lato”. A completely different classification was suggested by Shevyrev (2005), who divided cephalopods into eight subclasses. The subclasses itself comprise very different groups (paraphyletic/grade groups, plesions, and a crown group) many of them are considered as problematic and need serious revision [see here].

Who is currently working on fossil nautiloids sensu lato?

• Matilde S. Beresi, Mendoza, Argentina, (taxonomy of Middle Ordovician cephalopods, Argentine Precordillera, papers)
• Regis Chirat, Lyon, France (shell morphology and ontogeny of Mesozoic nautilids, papers)
• Marcela Cichowolski, Buenos Aires, Argentina (taxonomy of Ordovician cephalopods and Mesozoic nautilids, Southern Hemisphere, papers),
• David Evans, Peterborough, UK (taxonomy and phylogeny of Ordovician and Silurian cephalopods, UK, Ireland and cephalopods from former Gondwana, Avalonia, Perigondwana regions, papers)
• Robert C. Frey, Columbus, OH, USA (Upper Ordovician cephalopods of the USA, papers)
• Kathleen (Catherine) Histon, Italy (taxonomy of Late Carboniferous cephalopods Carnic Alps)
• Mauricio Gnoli (taxonomy and paleogeography of Silurian-Devonian cephalopods of Italy and the Carnic Alps,  papers)
• Christian Klug, Zürich, Switzerland (paleobiology of Triassic nautiloids of Germany, papers)
• Björn Kröger, Berlin, Germany (Paleoecology and Phylogeny of Paleozoic non-ammonoid cephalopods, with focus on the Early Paleozoic, papers)
• Stepan Manda, Praha, Czech Republic (taxonomy, paleoecology, paleogeography, phylogeny of Silurian-Devonian cephalopods of the Prague Basin, papers)
• Royal Mapes, Athens, OH, USA (Carboniferous-Permian cephalopods of the USA, bactritoid specialist, papers)
• Harry Mutvei, Stockholm, Sweden (cephalopod shell ultrastructure and siphuncular morphology with focus on Paleozoic nautiloids, papers)
• Shuji Niko, Higashihiroshima, Japan ( taxonomy of Late Paleozoic non-ammonoid cephalopods of Japan, papers),
• Ian G. Percival, Sydney, Australia (taxonomy and paleogeography of Australasian Ordovician cephalopods, papers)
• Jan Audun Rasmussen, Copenhagen, Denmark (Ordovician cephalopods of Greenland, and Norway)
• Voitech Turek, Praha, Czech Republic (taxonomy and phylogeny of Silurian-Devonian cephalopods of the Prague Basin, papers)
• Ryoji Wani, Yokohama, Japan  (Taphonomy of Nautilus, papers)
• Markus Wilmsen, Dresden, Germany (Cretaceous nautilids, papers)
• Cheol-Soo Yun, Kyungpook, Korea (taxonomy of Ordovician cephalopods of Korea, papers)
• Yunbai Zhang, Nanjing, China (Taxonomy and Morphology of Ordovician and Silurian cephalopods of China)

There are some anonymous workers (Theo Engeser, Berlin, is probably among them) which continuously complete, and keep up to date the fossil cephalopod pages at the  Palaeontology Portal of Wikipedia.
Austin Hendy, and me (very slowly) compile fossil cephalopod occurrences into the Paleobiology Database.

Current “hot” topics & interesting nautiloid papers

Living nautilids

Some of the remarkable papers about living nautiloids that appeared during the last years are: The complete mitochondrial genome of Nautilus macromphalus was published by Boore (2006).
Shigeno et al. (2008) analyzed the early development of Nautilus and suggested that early in ontogeny the morphology resembles the body plans of monoplacophorans and basal gastropods, and that the tentacles of Nautilus “develop from simple serial and spatially-patterned bud-like anlagen along the anterior-posterior axis, indicating that origins of digital tentacles or arms of all other cephalopods develop not from the head but from the foot.”
Crook et al. (2009) analyzed the spatial memory of Nautilus and found that its performance is comparable to coleoids.
Staples et al. (2000) demonstrated that Nautilus can suppress its metabolic rate 16-fold in low P O2, low temperature environments, supporting earlier evidence of an extremely high hypoxia tolerance of Nautilus.
Wani et al. (2008) reviewed the fossil history of Nautilus.
The taphonomic experiments of Wani and colleagues [2005, 2006, 2007] are important for the understanding of the interpretation of fossil cephalopod occurrences.

Aturia

The worldwide distribution and phylogeny of the Paleocene “goniatite” Aturia remains to be a discussed topic [Chirat, 2000; Nielsen et al., 2009]. Are the shells of Aturia drifted or represent the original distribution? A  paper of Tsujino and Iwata (2009) in Cretaceous Research reports a Late Creataceous Aturia from Japan.

Classification/Phylogeny

Orthocerida, Pseudorthocerida, Dissidocerida, Actinocerida – These orders are somehow related, but how, this is not clear. Are the orthocerids a paraphylum that consist partly of pseudorthocerids, dissidocerids, and actinocerids? Is there a higher monophyletic taxon, such as the “Orthoceratoidea” that includes all these orders plus the Lituitida (Mutvei, 2002)? In two papers by D. Evans [Evans, 2005] and me [2008] the Orthocerida and their relationships are discussed but no conclusion is reached. The revision in prep. of a Tremadocian cephalopod fauna with several orthocerids from the Montagne Noire by David Evans and me is promising. Orthocerids appear much earlier than previously thought and Bactroceras is now the earliest orthocerid, and neocephalopod. But because two very different transitional forms between ellesmerocerids and orthocerids exists already in the middle Tremadocian (Rioceras and Slemmestadoceras) a polyphyletic/paraphyletic origin of the orthocerid, and pseudorthocerid/actinocerid lineages cannot be excluded at the time.
Bactroceras is not related to Bactritites, the type of the Bactritoids. It is clear now, that bactritoids are only slightly younger than ammonoids, they evolved from Spaerorthocerids in the latest Lochkovian or Pragian [Kröger and Mapes, 2007].
The origin of the Nautilida is still an open question. But Manda and Turek [2009] revised the Rutoceratidae, coiled oncocerids that are probably the direct ancestors of the Nautilida and found evidence for a single monophyletic higher taxon of coiled oncocerids (the superfamily Rutoceratoidea) that strongly radiated during the Pragian.
As a consequence of these findings a major Early Devonian evolutionary pulse becomes visible during which pseudorthocerids [Kröger, 2008], and coiled oncocerids strongly radiated, and the bactritoids, the ammonoids, and probably also nautilids and coleoids had their first appearance.
Additionally the reviews in [Kröger and Landing, 2008; , Kröger et al. 2009], and my diversity analysis of Ordovician cephalopods reveal that during the narrow time interval between the middle Tremadocian and the early Floian, no less than 5 cephalopod orders had their first appearance; the Endocerida, Tarphycerida, Oncocerida, Orthocerida, and Discosorida.
Together these data show that the evolution of cephalopods during the Paleozoic was not a continuous process but occured in pulses (see also Kröger and Zhang, 2009).

Paleoecology

The first cephalopods of the pelagic realm appeared during the Tremadocian, pelagic cephalopods strongly diversified and became more common during the Middle Ordovician [Kröger et al. 2009]. This expansion of cephalopod habitat is parallel to other organism that entered the pelagic realm during the latest Cambrian-earliest Ordovician.

The Early Ordovician diversification of cephalopods was not only accompanied by an increase in disparity but by a general increase in cephalopod biomass at least at the shallow water carbonate platforms of the former Laurentia [Kröger and Landing, 2009].
The strong diversification of coiled shells during the Early Devonian is interpreted as adaptive response to an increased predatory pressure by durophages and as tendency toward an increased mobility of the nekton [Kröger, 2005; Manda and Turek, 2009; Klug et al in press; ].

Wish list

Morphological reconstruction

For many nautiloids sensu lato indirect data for soft body organization, and life habit are available (see e.g. Manda, 2007; Kröger, 2007), new data on the early ontogeny of Nautilus (Shigeno et al. 2007) would allow for nice reconstructions of ancient cephalopod, that could be used in popular presentations. Together with Slava Bizikov, I have a paper in prep. with reconstructions of some of them. Who will help us with its 3D/illustrative skills?

Treatise

The systematics of nautiloids sensu lato is partly messy (see for instance here, and here) and completely not to overview for a non-specialist. The Treatise is absolutely not up-to-date anymore, after more than 40 years since his publication. Lots of new genera were added since then and many taxa are revised. A new Treatise Nautiloidea is needed.

Paleogeography

Currently it is impossible to use Ordovician cephalopods for paleogeographic reconstructions because cephalopods from many paleo-regions of Gondwana and Perigondwana are in need of a revision or need to be described at all. Moreover, the (rich) Late Ordovician cephalopod faunas of Baltica are poorly described and lots of taxa are in the collections which never were described. These taxonomic descriptions and revisions are necessary in order to use cephalopods for reliable paleogeographic reconstructions.

“Wieso dauert das so lange?” Das werden da einige fragen, und: “Was hat er da eigentlich geschrieben?” Auf beides gebe ich gerne eine kleine Antwort.
Lange hat das gedauert, weil ich den Artikel zuerst in einer Zeitschrift, Palaeontology,eingereicht hatte, die ihn trotz positiver Reviews (die Gutachter haben den Artikel als Veröffentlichungswürdig mit “minor revisions” eingeschätzt) nicht haben wollten. Es ist sicher ein Artikel, der wenig zitiert wird. Da waren schon einmal drei Monate vergangen. Ich glaube im April 2008 habe ich dann das gute Stück bei Geobios eingereicht. Zugegebenermaßen, kein Open Access, aber das war mir nicht so wichtig, weil es eine Zeitschrift ist, die das Zielpublikum erreicht. Da hat es dann bis Januar gebraucht, im September hatte es der Editor geschafft, das Paper zu akzeptieren (Nachdem die gleichen Gutachter, die nun überarbeite Version jetzt vollends positiv bewertet haben). Dann kam ich in die Warteschleife, die nun heute beendet ist. Das Paper erschien (hier) und wer will kann es sich bei mir herunterladen (psst, nicht weitersagen).

Richardonoceras gastroscopium und Richardsonoceras goldmanni von Benedikt sind die beiden Namen, die ich schließlich von den Vorschlägen übernommen habe.

Der Artikel hat eigentlich nur den Zweck, diese neuen Formen zu beschreiben und in einen evolutionären Zusammenhang zu stellen. Es ist nichts Spektakuläres. Ich finde es aber wichtig diese Stücke zu beschreiben, weil sie zeigen, dass diese bestimmte Gruppe der Kopfüsser eine unerwartet, erdgeschichtlich frühe Formenvielfalt hat. Da es derzeit kaum Forscher gibt, die sich dafür interessieren ob, und wie sich diese Tiere entwickelt haben, ist der zu erwartende Zitationseintrag von dem Artikel eher gering. Aber wer weiß, vielleicht interressiert sich in 5 oder 10 oder 50 Jahren ja einmal jemand dafür und freut sich dann, darüber zu erfahren. Jetzt gibt es auf jeden Fall ein paar Tiernamen mehr.

The two papers are: (1) Shevyrev (2006) suggested a new higher classification of the fossil cephalopods, and (2) Barskov et al (2008) published a review of the palecology of Palaeozoic cephalopods.

The two articles appeared in the Russian “Paleontological Journal”. The Journal is not free available in the net. But the classification of Shevyrev (2006) is outlined at Wikipedia.

The “Paleontological Journal” is the English translation of the “Paleontologicheskii Zhurnal”, which is written and published in Russian, it is distributed by Springer. It is important to understand this when looking at the papers.

Shevyrev (2006) reviews the systematic nautiloid literature since Hyatt (1884). His article is quite good to get an overview of the different classification concepts since the late 19th century, but is is really bad when it comes to his new classification approach. Shevyrev’s own classification seems to lack any concept, it looks like he adapts the ideas of his predecessors when he likes the idea and he rejects it when he dislikes it. The problem with this approach is that he provides no criteria for its decisions, and in almost all cases no evidence for its statements. Moreover the classification provides no new data, whatsoever and is full of serious mistakes.

One good example is his decision of placing the Lituitida into the Nautiloidea. He discusses Starobogatov (1983), Dzik (1984) and Mutvei (2002). Dzik and Mutvei could add substantial new data to the Lituitid-Problem and proposed a new classification of the Litutitida together with the Orthocerida. Shevyrev summarized Mutvei (2002) completely wrong. Obviously he did not understand the Mutvei paper. Based on this misunderstanding he placed the Lituitida in the Nautiloidea.

Another example is his statement that the Orthocerida are the stem group of the subclass Orthoceratoidea. His sentence “The Order Orthocerida, which possesses all the above characters [viz. the characters of the Orthoceratoidea, BK], is the stem group of the subclass” shows his lack of knowledge what a stem group is (viz. a group that lacks substantial characters of the crown group).  Moreover the statement is wrong, because the Orthocerida have lost some characters, which are present in other members of the subclass (see Evans 2005). Orthocerida possess no cicatrix bearing apex.

There are many more misinterpretations,and serious mistakes in this paper and his higher classification of the palaeozoic nautiloids cannot be accepted. The question rises, how such flawed argumentation coul survive the review system of the Journal.

The Barskov et al. (2008) paper is strange in a way that it directly refers to nautiloid research from the 1960s and before, but completely lacks the review of work of many western scholars. Entire schools of thinking and research are completely ignored. The authors drew conclusions from their review. However, because this reviews is basically based on pre-1970s literature the results are in each case a clear drawback behind the work done since. Moreover, the papers is filled with statements without evidence. It seems that simply the authority of the author as a specialist is proof for the stated opinion.

I will give one example:, Barskov et al. discuss the orientation of the cephalopod shell during life, but fail to mention and discuss for example the major works and reviews of Rex Crick (1989) and Westermann (1998), which are really essential in this context.
The 100+ page paper has not a single reference of Westermann’s work who devoted dozens of articles and monographs on the mode of life, shell strength, locomotion etc of ammonoids and nautiloids (see e.g. references in Westermann, 1998, or do a simple Google search on G.E.G. Westermann).
The authors discuss the nautiloid buoyancy regulation with completely ignoring the work of Harry Mutvei, who published since the 1950s many important papers on the siphuncle morphology and buoyancy regulation of (again a simple google search gives dozens of hits).
Moreover, Barskov et al. (2008) is full of illustrations copied from other sources without referring to them. Probably the authors have no access to the literature or they are simply ignorant and this is the reason, why they produce bad science.

My question is: How can this be published in a peer review journal?

I think the answer is simple. Because, it was written originally in Russian, it was peer reviewed in Russian. And obviously there is no competent reviewer left in the Russian palaeontology. So one can question the review system of the “Paleontological Journal” in general. When the papers are published in English and the journal should be taken serious as an international journal they should run an international peer review.

Currently I would suggest simply to ignore these two papers, or read them with great care.

CRICK RE (1988) Buoyancy regulation and macroevolution in nautiloid cephalopods. Senckenbergiana lethaea 69:. 13-42.

EVANS, D. H., 2005, The Lower and Middle Ordovician cephalopod faunas of England and Wales. of the Palaeontographical Society Monograph, 158, 81 p.

WESTERMANN, G. E. G. 1998a. Life habits of nautiloids. In: Savazzi, E. (Ed.), Functional morphology of the Invertebrate skeleton, John Wiley & Sons, Chichester & New York, pp. 263–298.

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