Palaxius azulensis Kietzmann, 2010
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publication ID |
https://doi.org/ 10.4202/app.2009.0094 |
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persistent identifier |
https://treatment.plazi.org/id/A2018795-2140-FFB4-FCEE-FF54960FF8FB |
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treatment provided by |
Felipe |
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scientific name |
Palaxius azulensis Kietzmann |
| status |
sp. nov. |
Palaxius azulensis Kietzmann isp. nov.
Fig. 2A View Fig .
Etymology: Named after the Sierra Azul range, where the new ichnospecies was found.
Holotype: The specimen presented in Fig. 2A View Fig , thin section CPBA−N ° 20675.
Type locality: Rahue creek , Mendoza province, Argentina (36 ° 01.762'S, 69 ° 59.393'W) GoogleMaps .
Type horizon: Vaca Muerta Formation, Olcostephanus (Olcostephanus) atherstoni Zone , at approximately 340 m from the base.
Diagnosis.—Ichnospecies of the ichnogenus Palaxius with four internal canals clustered around a symmetry plane (2:2). It is differentiated from all other four−canaled Palaxius ichnospecies by the orientation of the canals ( Fig. 2A View Fig ).
Material.— Eight specimens: thin sections CPBA−N ° 20675, CCPBA−N ° 20676.
Description.—Rod−like microcoprolite with ventral groove and a cross section of 300 to 500 µm in diameter. Internally, it shows four canals. These are arranged bilaterally to the symmetry plane in two groups (2:2), each consisting of a dorsal canal (canal 1) and a ventral canal (canal 2). The canals have a crescent shaped outline, 100 µm long and 30 µm wide, with their concave side facing the symmetry plane, and with extremities characterised by rounded protuberances. Canal 1/1' is displayed at a 60 ° angle from the bilateral symmetry plane, while canal 2/2‘ is at a 90 ° angle ( Fig. 2 View Fig ).
Comparisons.— Palaxius azulensis Kietzmann isp. nov. differs from P. caucaensis Blau, Moreno, and Senff, 1995 , P. kumaensis Senowbari−Daryan and Silantiev, 1991 , P. tetraochetarius Palik, 1965 , and P. osaensis Buchs, Guex, Stucki, and Baumgartner, 2009 because of its cross−section morphology and the arrangement of the canals ( Fig. 3 View Fig ). The only ichnospecies with ventral groove and crescent−shaped canals with their concave side facing the symmetry plane is P. salataensis Brönnimann, Cros, and Zaninetti, 1972 , that can be distinguished by the orientation of canals 2 and 2’, which are orientated at 45 ° in P. salataensis and at 90 ° in P. azulensis in respect to the center of the microcoprolite.
Stratigraphic and geographic range.—The new ichnospecies was recognised at different levels corresponding to the Lissonia riveroi and Olcostephanus (Olcostephanus) atherstoni zones (Valanginian) in the Rahue creek and Yeso creek (Sierra Azul range) sections of the Vaca Muerta Formation ( Fig. 1 View Fig ). Other poorly preserved microcoprolites ( Favreinidae indet.) have been recognised in the Aulacosphinctes proximus (middle Tithonian) and Spiticeras damesi (late Berriasian) zones ( Fig. 1 View Fig ), so the presence of this ichnotaxon in levels of Tithonian and Berriasian age is possible.
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