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A revision of the Devonian Malvinokaffric dalmanitid trilobite Dalmanitoides Delo, 1935, on the basis of new data from Argentina

Juan J. Rustán and N. Emilio Vaccari

Plain Language Abstract

In this contribution we revise the Middle Paleozoic (Devonian) trilobite Dalmanitoides, on the basis of several new specimens coming from the Precordillera Basin of San Juan Province, in the pre-Andean region of Argentina. Thanks to detailed comparisons, it is concluded that Gamonedaspis is a junior synonym of Dalmanitoides, and consequently several species previously assigned to Gamonedaspis are considered to be Dalmanitoides representants. We provide precise information on the provenance data the type species D. drevermanni as well as for D. boehmi, another poorly known species.

Both species have been of interest in discussing closely related dalmanitid genera, mainly from South America and South Africa but the lack of sufficient material, revised diagnosis, and exhaustive descriptions, has precluded a reappraisal of their systematic, phylogenetic and paleobiogeographic significance. We conclude that these trilobites were restricted to southernmost marine areas during the Devonian (a paleobiogeographic area called the Malvinokaffric Realm), and they evolved rapidly into a great number of species during Devonian. Similar evolutionary patterns have been recognized in other coeval Malvinokaffric trilobites, which were already present in these basins since the Silurian. In our case the evidences suggest Devonian migrations as explanation of the origin of these dalmanitids trilobites in Malvinokaffric basins, because they are not known in older strata than Devonian.

Resumen en Español

Revisión del trilobite dalmanítido Dalmanitoides Delo, 1935, del Devónico malvinocáfrico, a partir de nuevos datos de Argentina

A la luz de nueva información sobre holotipos y material adicional proveniente de las áreas tipo del Devónico Inferior de Argentina, el trilobite Dalmanitoides Delo, 1935, es considerado un dalmanitino antes que un synphoriino. Las comparaciones sugieren que Gamonedaspis Braniša and Vaněk, 1973, es un sinónimo más joven de Dalmanitoides, de modo que este último género del Devónico Inferior a Medio, incluye al menos cinco especies: cuatro formalmente nominadas de Sudamérica, D. drevermanni (Delo, 1935), D. boehmi (Knod, 1908), D. scutata (Braniša and Vaněk, 1973) y D. accola (Clarke, 1913), junto con una especie de Sudáfrica tratada aquí en nomenclatura abierta (D. sp. A). Aunque el número de especies asignadas a Dalmanitoides sugiere así una diversificación de dalmanitinos cosmopolitas ya presentes en cuencas malvinocáfricas, la cercana relación con el género boreal y algo más antiguo Roncellia Lespérance and Bourque, 1971, indicaría una migración desde el Dominio del Este de las Americas durante el Devónico Temprano como origen del clado, lo cual está de acuerdo con patrones paleobiogeográficos reconocidos en base a la evidencia de distribución de synphoriinos.

PALABRAS CLAVE: trilobites dalmanítidos; Devónico; Argentina; Malvinocáfrico; Dalmanitoides; Gamonedaspis; sistemática; paleobiogeografía

Traducción: los autores

Résumé en Français

Une révision du trilobite dévonien malvinokaffrique dalmanitidé Dalmanitoides Delo, 1935, sur la base de nouvelles données provenant d’Argentine

A la lumière de nouvelles informations sur l’holotype et de matériel additionnel provenant de Dévonien inférieur de la région type d’Argentine, le trilobite dalmanitidé Dalmanitoides Delo, 1935, est re-diagnostiqué et considéré comme un dalmanitidé plutôt qu’un synphoriiné. Des comparaisons suggèrent que Gamonedaspis Braniša et Vaněk, 1973, est un synonyme de Dalmanitoides, de sorte que ce genre dévonien inférieur-moyen inclue au moins cinq espèces : quatre nommées formellement en Amérique du Sud D. drevermanni (Delo, 1935), D. boehmi (Knod, 1908), D. scutata (Braniša et Vaněk, 1973), et D. accola (Clarke, 1913), de même qu’une espèce d’Afrique du Sud traitée ici en nomenclature ouverte (D. sp. A). Bien que le nombre d’espèces de Dalmanitoides suggère que la diversification des dalmanitinés cosmopolites était déjà en place dans les bassins malvinokaffriques, une affinité forte avec le genre boréal et plus ancien Roncellia Lespérance et Bourque, 1971, suggérerait qu’une migration depuis le domaine paléobiogéographique d’Amérique de l’Est pendant le Dévonien inférieur serait à l’origine du clade, ce qui est en accord avec les schémas paléobiogéographiques reconnus sur la base de la distribution des synphoriinés.

MOST CLES : trilobites dalmanitidés ; Dévonien ; Argentine ; malvinokaffrique ; Dalmanitoides; Gamonedaspis; Systématique; Paléobiogéographique

Translator: Olivier Maridet

Deutsche Zusammenfassung

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Eine Revision des devonischen malvinokaffrisch-dalmanitischen Trilobiten Dalmanitoides Delo, 1935, auf Grundlage neuer wissenschaftlicher Untersuchungen in Argentinien

Vor dem Hintergrund neuer Information über Holotypen und zusätzlichem Material aus den unterdevonischen Typengebieten von Argentinien wird der dalmanitische Trilobit Dalmanitoides Delo, 1935, neu diagnostiziert und eher als dalmanitisch denn als synphoriinisch angesehen. Vergleiche zeigen, dass Gamonedaspis Braniša und Vaněk, 1973, ein Juniorsynonym von Dalmanitoides ist, so dass diese früh bis mitteldevonische Gattung zumindest fünf Arten beinhaltet: die vier offiziell aus Südamerika benannten D. drevermanni  (Delo, 1935), D. boehmi (Knod, 1908), D. scutata (Braniša and Vaněk, 1973) und D. accola (Clarke, 1913) zusammen mit einer Art aus Südafrika, hier aufgeführt in offener Nomenklatur (D. sp. A). Obwohl die Anzahl der Dalmanitoides-Arten eine Diversifikation der kosmopolitischen Dalmanitinen die bereits in den Malvinokaffrischen Becken präsent sind nahelegt, würde eine nahe Verwandtschaft mit der borealen und etwas älteren Roncellia Lespérance und Bourque, 1971 auf eine Migration aus den paläobiogeographischen Gebieten der östlichen Amerikas während des frühen Devon als Ursprung der Klade  hinweisen. Dies steht auch in Einklang mit paläobiogeographischen Mustern, die auf der Grundlage von Nachweisen synphoriinischer Verbreitung erkannt wurden.

SCHLÜSSELWÖRTER: dalmanitische Trilobiten; Devon; Argentinien; Malvinokaffrisch; Dalmanitoides; Gamonedaspis; Systematik; Paläobiogeographisch

Translators: Eva Gebauer and Anke Konietzka

Arabic

276 arab

Translator: Ashraf M.T. Elewa

Polski Abstrakt

Rewizja dewońskiego malvinokaffrycznego trylobita dalmanitydowego Dalmanitoides Delo, 1935 w oparciu o nowe dane z Argentyny

W świetle nowych informacji dotyczących holotypów i materiałów dodatkowych z wczesnodewońskich obszarów typowych Argentyny, dalmanitydowy trylobit Dalmanitoides Delo, 1935 poddany jest ponownej diagnozie i uznany raczej za dalmanityna, a nie synforiina. Porównania wskazują, że Gamonedaspis Braniša i Vaněk, 1973 to młodszy synonim Dalmanitoides, tak że ten wczesno-środkowodewoński rodzaj zawiera przynajmniej pięć gatunków: cztery formalnie nazwane z Ameryki Południowej, D. drevermanni (Delo, 1935), D. boehmi (Knod, 1908), D. scutata (Braniša i Vaněk, 1973) i D. accola (Clarke, 1913), wraz z gatunkiem z południowej Afryki, tutaj potraktowanym w otwartej nomenklaturze (D. sp. A). chociaż liczba gatunków Dalmanitoides sugeruje dywersyfikację kosmopolitycznych dalamnitynów obecnych wówczas w basenie Malvinokaffric, bliski związek z borealnym i nieco starszym Roncellia Lespérance i Bourque, 1971, wskazywałaby raczej na migrację z Królestwa Paleobiogeograficznego Wschodnich Ameryk w trakcie wczesnego dewonu jako momentu pojawienia się kladu, co jest zgodne z wzorcami paleobiogeograficznymi rozpoznanymi w oparciu o rozmieszczenie synforiinów.

SŁOWA KLUCZOWE: trylobity dalmanitydowe; dewon; Argentyna; Malvinokaffric; Dalmanitoides; Gamonedaspis; systematyka; paleobiogeografia

Translators: Dawid Mazurek and Robert Bronowicz

 

Anke Konietzka
 

FIGURE 1. Left: location map of the Central Argentine Precordillera basin, San Juan Province, western Argentina, showing Silurian-Devonian outcrops and fossiliferous localities. Right: the type area of Dalmanitoides drevermanni and D. boehmi at the Loma de los Piojos locality, to the southwest of Jáchal, shown in more detail.

Figure 1

FIGURE 2. Stratigraphic column of the Talacasto Formation at Loma de los Piojos section, where it is most developed. Column shows the stratigraphic position of the studied Dalmanitoides species in Devonian sedimentary succession. Dashed lines represent low abundance, complete lines correspond to most fossiliferous levels. Star shows probable location of type levels of Dalmanitoides drevermanni.

Figure 2

FIGURE 3. Cephala of Dalmanitoides drevermanni (Thomas, 1906). 1, 4, 6-7, 10-11 specimen CEGH-UNC 10499, partial cephalon: 1, internal mould dorsal view, 4, idem lateral view, 7, idem anterolateral dorsal view, 10, idem frontal view, 6, latex mould, dorsal view, arrows point to spiny processes on anterior border, 11, idem frontal view. 2-3, 5, 8, 12 specimen CORD-PZ 8615, partial cephalon: 2, internal mould, dorsal view, 5, idem lateral view, 8, idem anterolateral dorsal view, 12, detail of the anterior doublure and anterior margin, ventral view, 3, latex mould, dorsal view. 9 specimen CEGH-UNC 24304, partial cephalon, internal mould, dorsal view, arrow shows a spine on posterior border. Loma de los Piojos Section, Talacasto Formation, type early Emsian levels, San Juan Province, Argentina. Scale bar equals 5 mm.

fig3

FIGURE 4. Articulated specimens of Dalmanitoides drevermanni (Thomas, 1906). 1-6, CEGH-UNC 12738, outstretched articulated specimen, strongly compressed dorso-ventrally: 1, internal mould nearly complete, dorsal view, 2, latex cast, dorsal view, 3, detail of pleural lobes, internal mould, dorsal view, 4, latex cast, dorsolateral view, 5, detail of cephalon internal mould, dorsal view, 6, detail of occipital spine, dorsolateral view. Loma de los Piojos Section, Talacasto Formation, indeterminate levels, probably Pragian levels according to sandy lithology. 7, specimen CEGH-UNC 24309, two thoracic segments showing dorsal spine bases, type early Emsian levels, same section, San Juan Province, Argentina. Scale bar equals 5 mm.

Figure 4

FIGURE 5. Pygidia of Dalmanitoides drevermanni (Thomas,1906). 1-5, specimen CEGH-UNC 24307, partial pygidium, internal mould: 1, dorsal view, 2, lateral view, 3, posterior view, 4, posterodorsolateral view, 5, dorsolateral view. 6-10, 15, specimen CORD-PZ 8608, partial pygidum latex cast, 6, dorsal view, 7, lateral view, 8, posterior view, 9, posterodorsolateral view, 10, dorsolateral view, 15 detail of pleural field. 11-13, specimen CEGH-UNC 24313, partial pygidium latex cast, 11, dorsal view, 12, lateral view, posterior view. 14, specimen CEGH-UNC 24302, partial pygidium, internal mould, posterodorsolateral view. Loma de los Piojos Section, Talacasto Formation, 11-13 Pragian levels, all remaining type early Emsian levels, San Juan Province, Argentina. Scale bar = 5 mm.

Figure 5

FIGURE 6. Cephala of Dalmanitoides drevermanni? (Thomas, 1906). 1, 3-4, 6-9, 12, specimen CEGH-UNC 24318, 1, latex cast of partial cephalon, dorsal view, 3, internal mould, dorsal view, 4, latex cast, anterolateral view, 6, detail of anterior portion of cephalon, internal mould, 7, latex cast, anterolateral view, 8, anterolateral view, 9, lateral view, 12, frontal view. 2, 5, specimen CEGH-UNC 24324, partial cephalon: 2, dorsal view, 5, anterolateral view. 10, specimen CEGH-UNC 24327, latex cast of librigena, lateral view. 11, specimen CEGH-UNC 24324B, latex cast of a dalmanitine-type cheek showing a flat genal spine bearing a continuation of the epiborder furrow along its lower side. La Chilca section, Talacasto Formation, early Emsian levels, San Juan Province, Argentina. Scale bar equals 5 mm.

fig6

FIGURE 7. Cephala of Dalmanitoides boehmi (Knod, 1908). 1-4, specimen CEGH-UNC 24429, partial cephalon: 1, internal mould, dorsal view, note left S2 is effaced due to a malformation, 2, idem dorsolateral view, 3, idem anterodorsolateral view, 4, idem frontal view.5-9, specimen CEGH-UNC 24419, partial cephalon: 5, dorsal view, 6, idem lateral view, 7, detail of crenulated anterior margin, and anterior doublure, ventral view, 8, idem anterodorsolateral view, 9, frontal view. 10, specimen CEGH-UNC 24315, partial cephalon, internal mould, dorsal view. 11-12, specimen CEGH-UNC 24412, librigena showing the eye socle and the lateral doublure separated in a nearly sharp angle from the border (in cross section), 12 idem, dorsal view showing facial sutures. 13, specimen CEGH-UNC 24402, cheek showing the epiborder furrow, dorsal view. Loma de los Piojos Section, Talacasto Formation, Pragian levels under the guide horizon of Keidel (1921), San Juan Province, Argentina. Scale bar equals 5 mm.

Figure 7

FIGURE 8. Pygidia of Dalmanitoides boehmi (Knod, 1908). 1-4, specimen CEGH-UNC 24379, internal mould, 1, dorsal view, 2, idem lateral view, 3, idem posterior view, 4, idem posterodorsolateral view. 5-8, specimen CEGH-UNC 24331, internal mould, 5, dorsal view, 6, idem lateral view, 7, posterior view, 8, posterodorsolateral view. 9-12, specimen CEGH-UNC 24374, internal mould, dorsal view. 10, lateral view, 11, detail of mucro, posterolateral view, 12, posterodorsolateral view. 13, specimen CEGH-UNC 24380, partial pygidium, latex cast. 14, specimen CEGH-UNC 24378, partial pygidium, dorsal view, note evenly granulated surface of the carapace and tubercules on posterior pleural bands invading following anterior pleural bands backwards. 15, specimen CEGH-UNC 24377, pygidium with some thoracic segments attached, dorsal view, note tubercles on thoracic axial rings and long (exsag.) thoracic pleural furrows. Loma de los Piojos Section, Talacasto Formation, Pragian levels of the guide horizon of Keidel (1921) and immediately underlying, San Juan Province, Argentina. Scale bar equals= 5 mm.

Figure 8

FIGURE 9. Hypostome of D. boehmi. 1-4, specimen CEGH-UNC 24377, 1, latex cast, ventral view, 2, anteroventrolateral view, 3, detail of denticles on posterior margin, 4, lateral view. Loma de los Piojos Section, Talacasto Formation, Pragian (early Emsian?) levels of the guide horizon of Keidel (1921), preserved in a nodule together with a pygidium, San Juan Province, Argentina. Scale bar equals 5 mm.

Figure 9

FIGURE 10. Dalmanitoides boehmi (Knod, 1908). 1, scanned copy of the original drawing published by Knod (1908, p. 567, figure 21.1). 2, the original holotype specimen collected by Hauthal from the Talacasto Formation, to the southwest of Jáchal, probably Pragian strata, to the west of Loma de los Piojos section, San Juan. Presently housed at University of Freiburg (Institut für Geowissenschaften-Geologie, repository number: 2778), Freiburg, Germany. Probably an internal mould, dorsal view. Note that the original fossil is either idealized in the drawing or suffered damage after it was published. Scale bar equals 5 mm.

Figure 10

FIGURE 11. Dalmanitoides accola (Clarke, 1913). 1, specimen NYSM 12069 , cephalon, dorsal view, note lack of crenulation on anterior border anterolaterally. 2, specimen NYSM 12072, cephalon, internal mould, dorsal view. 3, specimen NYSM 12077, cephalon, anterolateral view, note the rounded median projection of the anterior border. 4, specimen NYSM 17262 , skeletal associated parts (moult ensemble?), dorsal view, note the irregular distribution of coarse to spinose tubercles on pygidial axial rings. 5, specimen NYSM 17304, nearly articulated specimen, dorsal view. 6, specimen NYSM 17466, pygidium, internal mould, dorsal view. 7, specimen NYSM 17467, external mould of pygidium, dorsal view. Lower Devonian, Ponta Grossa Formation, Paraná, Brazil. Scale bar equals 5 mm.

Figure 11

 

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Juan Jose RustanCIPAL - CICTERRA (Facultad de Ciencias Exactas Físicas y Naturales
Universidad Nacional de Córdoba - CONICET)
Av. Vélez Sársfield 299
5000, Córdoba,
Argentina
and
Museo de Ciencias Naturales
Universidad Nacional de La Rioja
Av. René Favalor
s/n 5300- La Rioja
Argentina

Juan José Rustán graduated in Law (2000) from Catholic University of Córdoba (Córdoba province, Argentina), and later (2006) received a Licenciature in Biology with orientation in Paleontology at University of La Plata (Buenos Aires province). At present (2011), he is granted by CONICET (National Research Council of Argentina) for concluding his PhD thesis (Geological Sciences) on Devonian trilobites from Argentina, at National University of Córdoba. Together with his PhD advisor, N. Emilio Vaccari, he also teachs Paleontology at University of La Rioja (La Rioja province). He is particularly interested in systematic, phylogenetic, biostratigraphic and paleobiogeographic aspects of Devonian trilobites, and his scientific contributions are focused in western Gondwanan faunas of the Malvinokaffric Realm.

This email address is being protected from spambots. You need JavaScript enabled to view it.
N. Emilio VaccariCIPAL - CICTERRA (Facultad de Ciencias Exactas Físicas y Naturales
Universidad Nacional de Córdoba - CONICET)
Av. Vélez Sársfield 299
5000, Córdoba
Argentina
and
Museo de Ciencias Naturales
Universidad Nacional de La Rioja
Av. René Favaloro
s/n 5300- La Rioja
Argentina

N. Emilio Vaccari is professor of paleontology of the National University of La Rioja, Argentina and researcher of CONICET (National Research Council of Argentina). Geologist (1987) and PhD in Geological Sciences (1994), from the National University of Córdoba, Argentina. He is author or co-author of numerous contributions on systematic, phylogeny, biostratigraphy and paleobiogeography of Lower and Middle Paleozoic trilobites, mainly focused on South American faunas.