Invertebrate Zoology, 2017, 14(1): 27–31 © INVERTEBRATE ZOOLOGY, 2017

Evolution of Palaeozoic ammonoid sutures

T.B. Leonova

Borissiak Paleontological Institute of the Russian Academy of Sciences. 123, Profsoyuznaya str., Moscow, 117647, Russia. E-mail: [email protected]

ABSTRACT. The history of the appearance and evolution of the suture, one of the major structural elements of the shells of ammonoids (a subclass of Cephalopoda), is briefly discussed. Its morphology is considered in the Devonian Anarcestida, the first members of which are very similar to the ancestral Bactritoidea, in the Late Devonian Clymeniida, the Devonian–Permian Tornoceratida, the Carboniferous–Permian Prolecanitida and Goni- atitida, and the Permian Ceratitida. Three major trends in the evolution of the suture are recognized in the order Goniatitida, which were instrumental in the subdivision of this order into suborders. Variations of elements of the sutures allow the recognition of the familial, generic, and specific ranks. How to cite this article: Leonova T.B. 2017. Evolution of Palaeozoic ammonoid sutures // Invert. Zool. Vol.14. No.1. P.27–31. doi: 10.15298/invertzool.14.1.05

KEY WORDS. Ammonoids, Paleozoic, evolution, sutures, systematics.

Эволюция лопастных линий у палеозойских аммоноидей

Т.Б. Леонова

Палеонтологический институт им. А.А.Борисяка РАН, Профсоюзная, 123, Москва, 117647 Россия. E-mail: [email protected]

РЕЗЮМЕ: Кратко изложена история становления и развития в палеозое лопастной линии, одного из основных структурных элементов раковины аммоноидей (подклас- са цефалопод). Показаны особенности ее строения у девонских Anarcestida, первые представители которых очень близки к своим предкам Bactritoidea, своеобразных позднедевонских Clymeniida, девонско–пермских Tornoceratida, каменноугольно- пермских Prolecanitida и Goniatitida, пермских Ceratitida. В рамках отряда Goniatitida выделено три главных направления развития лопастной линии, которые находят свое выражение в подразделении отряда на три подотряда. Изменения отдельных элемен- тов лопастной линии позволяют выделять таксоны семейственного, родового и видового ранга. Как цитировать эту статью: Leonova T.B. 2017. Evolution of Palaeozoic ammonoid sutures // Invert. Zool. Vol.14. No.1. P.27–31. doi: 10.15298/invertzool.14.1.05

КЛЮЧЕВЫЕ СЛОВА: Аммоноидеи, палеозой, эволюция, лопастные линии. 28 T.B. Leonova

monoids. The general sutural outline is charac- teristic of orders and families, whereas its finer details are characteristic of genera and species. The development of a complexly curved septum and fluted dissected suture is the main trend in the evolution of Ammonoidea. The sutural on- togeny retained in the early whorls allows reli- able reconstructions of the phylogeny of closely related taxa.

Fig. 1. A shell of Agathiceras mediterraneum Tou- Material and methods manskaya, 1949, Kungurian, Early Permian, showing a phragmocone (with sutures on its surface) and a Despite the technological advances and the body chamber. A — lateral view; B — apertural view. availability of micro-computed tomography, Рис. 1. Раковина Agathiceras mediterraneum Tou- ammonoid sutures are mainly studied using a manskaya, 1949, кунгур, ранняя пермь. Видны light microscope equipped with a drawing arm фрагмокон (с лопастными линиями на поверхно- (camera lucida) to obtain graphic drawings (the сти) и жилая камера. method used for this study). These drawings A — вид с боковой стороны; B — вид со стороны устья. were then scanned and print–ready copies were produced using graphics software, e.g., Introduction CorelDraw. The sutural outlines produced in this way were scaled, and then analyzed and The ammonoids appeared approximately 400 compared. The elements of the sutures were million years ago, at the end of the Early Devo- designated using the terminology of Ruzhencev nian, and after 335 million years of evolution (1960). The study was based on the collections became extinct at the Mesozoic–Cenozoic of Paleozoic ammonoids housed in the Boris- boundary. For two hundred years they were siak Paleontological Institute, Russian Acade- used by palaeontologists as model objects to my of Sciences, and on some previous literature study morphogenesis and phylogeny. Their com- sources. plexly organized shell retaining all ontogenetic stages allows reconstruction of phylogenies of Results and Discussion groups of various systematic ranks. The body plan of ammonoids includes three The research of several generations of palae- main morphological parameters: a coiled shell, ontologists allows the evolution of the sutures to a complex suture, and the presence of a proto- be traced in all Paleozoic orders. In very general conch. The ammonoid shell was subdivided terms, the results of this research can be summa- into a body chamber (from 0.5 to 1.5 whorls) rized as follows. In the Emsian, at the end of the and a phragmocone working as a buoyancy Early Devonian, representatives of the subclass device. Paleontologists usually study ammonoid Ammonoidea had a two-lobed suture inherited sutures formed on the shell surface as an expres- from bactritoids (designated by the formula sion of the intersection of septa (Fig. 1). The VO, i.e., ventral and omnilateral lobes (cover- sutures include lobes (expressions of curved ing the entire flank); these are the earliest am- surfaces directed adorally) separated by orally monoid genera Anetoceras, Erbenoceras, Te- directed saddles. The lobes can be simple, ser- icherticeras, etc. (order Anarcestida, family rated, festooned, etc., whereas the saddles are Anetoceratidae) (Fig. 2). The next stage is the most frequently simply rounded. The sutural appearance of a dorsal lobe (formula VO:D), outlines are taxon-specific, and are used as the which occurred at the end of the Emsian (genera main diagnostic character for Paleozoic am- Mimosphinctes, Talenticeras family Mimo- Evolution of Palaeozoic ammonoid sutures 29

Fig. 2. Evolution of the Paleozoic ammonoid sutures. Рис. 2. Эволюция лопастных линий аммоноидей в палеозое. sphinctidae, etc.). At the very end of the Emsian, the hatchling and by the morphology of several in the order Anarcestina (family Anarcestidae, subsequent septa, in which the number and genera Anarcestes, Cabrieroceras, Archocer- arrangement of lobes is considered to be funda- as, etc.), the omnilateral lobe was replaced by mental for the definition of the body plan of the the umbilical (U), the formula of the suture is mollusk. VU:D (Fig. 2). In the Middle Devonian (Give- Almost the entire diversity of the septal tian), representatives of suborder Gephurocera- margins (sutures) can be found among Anarces- tina (genus Tamarites, etc.) acquire the inner tida (Early Devonian, Emsian — end of the lateral lobe (I); such sutures are described by the Devonian) known to exist in Paleozoic am- formula VU:ID. The external lateral lobe (L) monoids, with the exception of the complexly appeared in the Middle Devonian, when the subdivided sutures of the “Mesozoic type” that four-lobed (VLU:D) order Tornoceratida (ge- appeared at the end of the Paleozoic. For exam- nus Tornoceras, etc.) appeared. In the Late ple, a broad, tripartite ventral lobe appeared in Devonian (Famennian) five-lobed (VLU:ID) the Early Devonian in the suborder Auguritina. Sporadoceratidae (Sporadoceras, etc.) appeared Later, in the Late Devonian, this character reap- (Fig. 2). All subsequent sutural modifications peared in the members of the suborder Ge- appeared on the basis of these five main lobes, phuroceratina. In some Gephuroceratina, the which define the current system of the subclass suture was very complex due to the appearance Ammonoidea. of additional ventral or umbilical lobe (up to 54 The suture type is defined by the morpholo- lobes around a whorl). In members of the subor- gy of primary suture formed by a rear mantle of der Timanoceratina, the ventral lobe was bipar- 30 T.B. Leonova tite. In general, most members of the oldest ognized based on the fundamental differences ammonoid order have the suture described by in the development of the primary lateral lobe the sutural formula VU:D (Bogoslovsky, 1969). (L) and umbilical (U) lobe: Goniatitina, Adrian- Members of the order Clymeniida, which itina, and Cyclolobina. In representatives of the existed only for a very short time (the very end suborder Goniatitina, the total number of lobes of the Devonian (Famennian)) were strikingly in the suture remained eight almost throughout different from all other ammonoids. Instead of their history (genera Glaphyrites, Paragastrio- the ventral lobe they had a ventral saddle result- ceras, etc), with the exception of some Schisto- ing from the dorsal, rather than the ventral, (as ceratoidea (Carboniferous), with a suture in in most ammonoids) siphuncle (genus Clyme- which the umbilical lobe U was further subdi- nia, etc). Following the “archaic diversity” of vided. In the majority of Goniatitina, the sutural the sutures of Devonian ammonoids assigned to complexity increased by altering the width and the order Anarcestida with five suborders and depth of main lobes, less commonly by develop- Clymeniida with two suborders (Shevyrev, ment of teeth and projections on the main lobes, 2006), four large groups were formed by the without forming new elements. The margins of beginning of the Carboniferous, each character- the lobes and saddle usually remained entire. ized by a particular evolutionary trend and re- The two youngest families Metalegoceratidae ceiving an ordinal rank. (Early Permian) and Spirolegoceratidae (Mid- The order Prolecanitida had previously been dle Permian, Roadian) increase their sutural included in the Devonian order Agoniatitida complexity throughout a division of the primary (Ruzhencev, 1960; Bogoslovsky, 1969, etc.), umbilical lobe. The most derived members of because it was thought that in this order the most these families had a suture with 12–16 lobes. primitive suture consisted of three lobes VU:D. This increased complexity was achieved first by Studies of recent decades (Zakharov, 1984; partial, then by complete subdivision of the Leonova and Voronov, 1989; Korn et al., 2002) umbilical lobe into three. It should be noted that showed that in prolecanitids the suture could be in all ammonoid groups, the umbilical portion three-lobed (VU:D), four-lobed (VU:ID), and of the suture was the most mutable. sometimes five-lobed (VLU:ID). In members The second group, the suborder Adrianitina of this order, the ventral lobe (V) was narrow, (Late Carboniferous, Kasimovian — Middle deep, tripartite, while the dorsal lobe was nar- Permian, Capitanian) has a complex suture, row and bipartite (genera Prolecanites, Epican- which was formed in a very unusual way: unlike ites, Pronorites, Medlicottia, etc). The main all other suborders, new umbilical lobes were evolutionary trend in this order was manifested by increased complexity of the external saddle formed at the top of the umbilical saddle and and of the number of lobes on the flanks up to 20 moved alternately first to the inner, and then to (Fig. 2). It is likely that this group of Paleozoic the outer sides of the whorl, following the for- mula (V V )LU:ID (V V )LUU2:U1ID ammonoids gave rise to the Mesozoic Ceratiti- 1 1 → 1 1 → (V V )LUU2Un+1:UnU1ID (genera Emilites, Cri- da at the Early–Middle Permian boundary. 1 1 The order Goniatitida (sensu Ruzhencev mites, Adrianites, etc). Neither external, nor (1960), Bogoslovskaya et al. (1990), Bog- internal lateral lobes were subdivided. Margins oslovsky (1971) and other authors) is currently of all lobes remained entire. This group branched subdivided into three separate orders based on off the Goniatitina by the beginning of the Late the mode of development of the ventral lobe Carboniferous, but its main evolution was in the (V): order Goniatitida (V — always bipartite), Permian (Fig. 2). order Tornoceratida (V — in most cases undi- The most advanced goniatitids, representa- vided), and Praeglyphioceratida (V — broad tives of the suborder Cyclolobina (late Carbon- and tripartite) (Leonova, 2002). iferous, Gzhelian — end of the Permian, Chang- The order Goniatitida (Tournaisian–Chang- hsingian), had the most complex sutures. Their hsingian) includes three groups (suborders) rec- sutures showed a primary subdivision of the Evolution of Palaeozoic ammonoid sutures 31

lateral lobe following the formula L → (L2L1L2) This is a brief history of the evolution of the

→L2L1L2, and in some groups, a further subdi- Paleozoic ammonoid sutures, one of the major vision of the third external lateral lobe. The structural elements of the shell. It is evident that inner lateral lobe (I) and umbilical (U) lobe in changes in the sutural outlines were controlled different superfamilies also underwent tripar- by a large system of organismal functions and tite or bipartite subdivision and in different communications, which maintained a certain branches these changes followed different pat- stability and at the same time were initiated by terns. In addition, in all groups the lobes and external factors. saddles possess numerous digits and arches. This suborder includes the superfamilies with Acknowledgements the most complex sutures (the total number of The study was supported by the Program No lobes in the suture reached 60): Cycloloboidea 28 of the Presidium of the Russian Academy of (genera Demarezites, Timorites, Cyclolobus, Sciences “Evolution of the Organic World and etc.), Shumarditoidea, Marathonitoidea (genus Planetary Processes” (subprogram 2). Marathonites, Cardiella, etc), and Popanocera- toidea (genus Popanoceras, Neopopanoceras, References etc.) (Fig. 2). Bogoslovskaya M.F., Mikhailova I.A., Shevyrev A.A. The first Ceratitida appeared at the Early– 1990. [System of ammonoids] // V.V. Menner (ed.). Middle Permian boundary. Members of this, Sistema i filogeniya bespozvonochnykh. Moscow: mainly Mesozoic order show a development from Nauka. P.69–98 [in Russian]. Bogoslovsky B.I. 1969. [Devonian ammonoids. 1. Ago- a three-lobed primary suture (in Middle Permian nititida] // Trudy Paleontologicheskogo Instituta AN Paraceltitina, genus Paraceltites) VU:D to the SSSR. Vol.124. 328 p. [in Russian]. five-lobed suture VLU:ID, and later the umbili- Bogoslovsky B.I. 1971. [Devonian ammonoids. 2. Goni- atitida] // Trudy Paleontologicheskogo Instituta AN cal lobe disappears (VL:ID), while an additional SSSR. Vol.127. 228 p. [in Russian]. 1 Korn D., Ebbighausen V., Bockwinkel J., Klug C. 2003. inner lobe appears at later stages (V1V1)LII : (D D ). Late Permian Paraceltitina have a four- The A-mode sutural ontogeny in Prolecanitid am- 1 1 monoids // Palaeontology. Vol.46. Part 6. P. 1123– lobed primary suture VL:ID (genera Paratiroli- 1132. tes, Xenodiscus, etc) (Fig. 2). A further increase Leonova T.B. 2002. Permian ammonoids: Classification in complexity occurs with the development of and Phylogeny // Paleontological Journal. Vol.36. Suppl.1. P. S1–S114. 1 2 new umbilical lobes (V1V1)LU U :II(D1D1). This Leonova T.B. 2016. Normal range and variation in the mode of increase in complexity marks a funda- ontogeny of the Late Paleozoic ammonoid family mental difference of Ceratitida from Prolecan- Marathonitidae // Paleontological Journal. Vol.50. No.14. P.1579–1586. itida and Goniatitida (Shevyrev, 1986). Leonova T.B., Voronov A.V. 1989. Sutural ontogeny of More detailed changes in various elements the Early Permian ammonoid genus Synartinskia // of the ammonoid shell are usually taken into Paleontologicheskii Zhurnal. No.1. P. 113 –116 Ruzhencev V.E. 1960. [Principles of systematics, system account in classifying taxa of lower taxonomic and phylogeny of Paleozoic ammonoids] // Trudy ranks: families, genera, and species. Usually Paleontologicheskogo Instituta AN SSSR. Vol.33. Paleozoic ammonoids have a stable sutural pat- 331 p. [in Russian]. Shevyrev A.A. 1986. [Triassic ammonoids] // Trudy Pale- tern within the same taxon. Nevertheless, there ontologicheskogo Instituta AN SSSR. Vol.217. 184 p. are cases of asymmetrical development of lobes [in Russian]. and saddles on different sides of the same shell, Shevyrev A.A. 2006. Macrosystem of cephalopods: his- torical review, current state and major problems. 3. formation of additional digits and small lobes in Classification of bactritoids and ammonoids // Pale- the umbilical region (Leonova, 2016). The study ontological Journal. Vol.40. No.2. P.34–46. of ammonoid sutures reveals cases of parallel Zakharov Yu.D. 1984. [Ontogeny of Permian Pronoritidae and Medlicottiidae and the problem of the origin of development (synchronous and asynchronous), ceratitids] // Sistematika i evolyutsiya bespozvonoch- heterochronies, recapitulation, paedomorpho- nykh Dalnego Vostoka. Vladivostok: DVNTs AN sis, mosaic forms, which are all used in recon- SSSR. P.23–40 [in Russian]. structions of morphogenesis. Responsible editor E.N. Temereva