Ptyctodontida

Ptyctodontida
	Materpiscis attenboroughi
Temporal occurrence
	Upper Devonian
	383.7 to 360.7 million years
Locations
	North America, Europe, Asia, Australia; Algeria, Libya;
Systematics
	Chordates (chordata)
	Vertebrates (vertebrata)
	Placodermi
	Ptyctodontida
Scientific name
	Ptyctodontida
	Gross , 1932

The Ptyctodontida (Ptyctodontidae) are a group of the extinct placodermi , fish-like, armored vertebrates from the Devonian . Most of them lived in the sea and were less than eight inches long. Isolated, 15 to 20 centimeter long tooth plates, which were found in North America near New York , suggest a very large species with a length of 2.5 meters.

features

Ctenurella gladbachensis is an approx. 19 cm long shell fish from the Strundetal in the Paffrath Kalkmulde . The species epithet refers to the Bergisch Gladbach site .

Of all placoderms, they most closely resemble modern fish. Her head was big with big eyes. The head armor only encloses the rear part of the skull. The torso armor is short and enabled the animals to perform winding movements with their torso and tail, similar to today's eels. The unarmored fuselage was slender and flaky, the tail fin reduced to a low hem. The fish had two dorsal fins , and in some forms the front was supported by a spiky, elongated part of the body armor. The second dorsal fin was elongated and supported by many fin rays. Of all placoderms, the ptyctodontids were probably the most active swimmers.

The animals each have two characteristic tooth plates in the upper and lower jaw. The animals probably fed on hard-shelled, soil-dwelling organisms. The upper jaw is made up of three bones connected by cartilage, each connected to the neurocranium . At the back of the head there are indications of four gill arches. The joint between the head and trunk armor is not as pronounced as in the arthrodiruses . Lip and rostral cartilages are similar to those of sharks and sea cats .

The Ptyctodontida are the only placoderms to show sexual dimorphism . In the males, the pelvic fins were transformed into two prickly mating organs (pterygopodia) that served for internal fertilization, a feature that is unique within the placoderms. In the Ptyctodontid Materpiscis attenboroughi , discovered in Australia in 2008 , the remains of an embryo were discovered that reached about a quarter of the length of the approximately 25 centimeters large mother and was connected to it by an umbilical cord. Materpiscis thus shows the oldest evidence of viviparity (live births).

Systematics

The Ptyctodontida resemble today's sea cats (Chimaeriformes) in their external appearance . A kinship has also been assumed by some scientists. Others believe that the similarities are due to convergence and not a relationship. The pterygopodia of the Ptyctodontida also differ from the clusters of the Chimaeriformes.

The taxon was established in 1932 by Walter Robert Gross . The cladogram shows the systematic position of the ptyctodontida within the placodermi according to King et al. , 2017.

Placodermi

	Antiarchi

	Brindabellaspis stensioi

Diandongpetalichthys liaojiaoshanensis

	Petalichthyida

	Ptyctodontida

Arthrodira

Rhenanida

Systematic position of the ptyctodontida within the placodermi, simplified from King et al., 2017.

Genera:

literature

Joseph S. Nelson: Fishes of the World . John Wiley & Sons, 2006, ISBN 0-471-25031-7
Robert L. Carroll: Paleontology and Evolution of the Vertebrates . Thieme, Stuttgart 1993, ISBN 3-13-774401-6
John A. Long: The Rise of Fishes . The Johns Hopkins University Press, 1995, ISBN 0-8018-4992-6

Web links

Palæos Ptyctodontida

Individual evidence

↑ Hans Martin Weber: World-famous fish and crabs from the Devonian of the Strundet valley in Bergisch Gladbach , In: Schriften der Bodendenkmalpflege in NRW , Volume 9, Ed. Thomas Otten , Römisch-Germanisches Museum der Stadt Köln and Verlag von Philipp Zabern, Mainz 2010, P. 24 ff. ISBN 978-3-8053-4204-9 .
^ John A. Long, Kate Trinajstic, Gavin C. Young, Tim Senden: Live birth in the Devonian period . In: Nature , Volume 453, 2008, pp. 650-652 doi: 10.1038 / nature06966 ( abstract ).
^ WR Gross: The Arthrodira Wildungen. In: Geologische und Paläontologische Abhandlungen, New Series , Volume 19, 1932, pp. 1–61.
↑ ^a ^b B. King, T. Qiao, MSY Lee, M. Zhu & JA Long: Bayesian Methods Morphological Clock Resurrect placoderm monophyly and Reveal Rapid Evolution Early in Jawed Vertebrates. In: Systematic Biology , Volume 66, Number 4, 2017, pp. 499-516, ( digitized ).

[Weber,_2010-1] Hans Martin Weber: World-famous fish and crabs from the Devonian of the Strundet valley in Bergisch Gladbach , In: Schriften der Bodendenkmalpflege in NRW , Volume 9, Ed. Thomas Otten , Römisch-Germanisches Museum der Stadt Köln and Verlag von Philipp Zabern, Mainz 2010, P. 24 ff. ISBN 978-3-8053-4204-9 .

[Long_et_al.,_2008-2] John A. Long, Kate Trinajstic, Gavin C. Young, Tim Senden: Live birth in the Devonian period . In: Nature , Volume 453, 2008, pp. 650-652 doi: 10.1038 / nature06966 ( abstract ).

[Gross,_1932-3] WR Gross: The Arthrodira Wildungen. In: Geologische und Paläontologische Abhandlungen, New Series , Volume 19, 1932, pp. 1–61.

[King_et_al.,_2017-4] B. King, T. Qiao, MSY Lee, M. Zhu & JA Long: Bayesian Methods Morphological Clock Resurrect placoderm monophyly and Reveal Rapid Evolution Early in Jawed Vertebrates. In: Systematic Biology , Volume 66, Number 4, 2017, pp. 499-516, ( digitized ).