Coastal raptors and raiders (1 Viewer)

[Fred Ruhe]

Neto de Carvalho, C.; Belo, J.; Figueiredo, S.; Cunha, P. P.; Muñiz, F.; Belaústegui, Z.; Cachão, M.; Rodriguez-Vidal, J.; Cáceres, L. M.; Baucon, A.; Murray, A. S.; Buylaert, J.-P.; Zhang, Y.; Ferreira, C.; Toscano, A.; Gómez, P.; Ramírez, S.; Finlayson, G.; Finlayson, S.; Finlayson, C. 2023

Coastal raptors and raiders: New bird tracks in the Pleistocene of SW iberian Peninsula

Quaternary Science Reviews : Volume 313, 1 August 2023, 108185

Avian traces occurring in Pleistocene aeolianite and beach deposits are rare and relatively poorly known, despite being good paleoenvironmental indicators. Passeriform and raptorial birds are especially rare in the track fossil record. Exceptional tracksites were found in the Malhão formation, a Pleistocene coastal aeolianite unit from the SW mainland Portugal, with subunits in the interval ∼187 to ∼27 ka. Two new forms of avian traces were identified, Corvidichnus odemirensis and Buboichnus vicentinus - attributed to the locomotion of Western jackdaw and the locomotion and predation/feeding behaviour of a large Eagle-owl. The last trace fossil may correspond to the first evidence of a raptorial bird-prey interaction found in action in the fossil record. Typical shorebird tracks and trackways attributed to gulls (Laridae) and curlews, and others tentatively compared with Rallidae, such as Eurasian coot, are also discussed within the aeolianite ichnoassemblages. The tracks here described are the first avian ichnotaxa from the Pleistocene of Europe.
Avian traces occurring in Pleistocene aeolianite and beach deposits are rare and relatively poorly known, despite being good paleoenvironmental indicators. Passeriform and raptorial birds are especially rare in the track fossil record. Exceptional tracksites were found in the Malhão formation, a Pleistocene coastal aeolianite unit from the SW mainland Portugal, with subunits in the interval ∼187 to ∼27 ka. Two new forms of avian traces were identified, Corvidichnus odemirensis and Buboichnus vicentinus - attributed to the locomotion of Western jackdaw and the locomotion and predation/feeding behaviour of a large Eagle-owl. The last trace fossil may correspond to the first evidence of a raptorial bird-prey interaction found in action in the fossil record. Typical shorebird tracks and trackways attributed to gulls (Laridae) and curlews, and others tentatively compared with Rallidae, such as Eurasian coot, are also discussed within the aeolianite ichnoassemblages. The tracks here described are the first avian ichnotaxa from the Pleistocene of Europe.

Enjoy,

Fred

 

[Fred Ruhe]

Systematic ichnology

Ichnogenus Corvidichnus igen. Nov.

Type ichnospecies: Corvidichnus odemirensis isp. Nov.

Derivatio nominis: The ichnogenus name includes the family Corvidae Vigors after the inferred type of producers and “ichnus” for trace. The specific name recalls the Odemira municipality where these tracks were found.

Diagnosis: Bipedal trackway of high pace angulation with mesaxonic tetradactyl, anisodactyl tracks of moderate size with small positive rotation with the midline. Tracks with three compared-sized digits directed forward showing clear phalangeal pad impressions, and a long hallux pointing backward, but slightly offset from the middle line; divarication angles between digits II-IV are small (i.e. ~70); track length/width ratio less than 2.

Corvidichnus odemirensis isp. Nov.

Holotype: A trackway of 4 footprints left in situ (T1C0 marked with yellow in Fig. 4). 3D digitype available as supplementary material (Sketchfab link: xxxxx).

Diagnosis: Same as for the ichnogenus, for now the only known ichnospecies.

Horizon and locality: Malh~ao formation located at Aivados Sul beach, coordinates 3747026.7700N 848007.5800O; Chibanian (OSL dating of 187 ± 11 ka for the lower part of the Malh~ao formation at Pessegueiro Island).

Remarks: By their morphology these are typical tracks of large perching birds, without any doubt compared with corvids (see discussion). The asymmetric ripples and the direction of the trackways indicate that the bird(s) walked following the wind direction. There is also a nice trackway of the rabbit Oryctolagus cuniculus that was identified at the near Malhao beach as Leporidichnites malhaoi by Neto de Carvalho (2009).

Ichnogenus Gruipeda Panin and Avram.

Diagnosis: Tracks showing four digits, three (II to IV) directed forward and long; toe I pointing backwards, spur-like and short. The interdigital angles between digits II and III and digits III and IV
are less than 70. The axis of digit I does not correspond with that of digit III, the interdigital angle between digits I and II is greater than that between digits I and IV. Webbing absent (emended by Sarjeant and Langston, 1994).

Gruipeda aff. maxima Panin and Avram.

Ichnogenus Buboichnus igen. Nov.

Type ichnospecies: Buboichnus vicentinus isp. Nov.

Derivatio nominis: The ichnogenus name after the species Bubo bubo (Linnaeus), the likely producer, and “ichnus” for trace. The specific name recalls to cape Sao Vicente where these tracks were found.

Diagnosis: Moderate-sized tetradactyl zygodactyl tracks with well-developed hallux impression; digital pads recognizable and with claw marks attached or independent. Digits II and III point anteriorly with digits I and IV pointing posteriorly with variable divarication angle, but showing mesaxonic symmetry.

Buboichnus vicentinus isp. Nov.

Holotype: Paired-tracks TZTrk006 L and TZTrk007/8 R in Fig. 7. 3D digitype available as Supplementary Material (Sketchfab link xxxx).

Diagnosis: The same as for the ichnogenus.\]

Horizon and locality: Telheiro aeolianite located in the Quebrada creek close to the beach, coordinates 3702051.0700N 858012.7900O. Taking in account that the horizon with the bird tracks is located between dated levels by 14 C dating (44.7 and 40.3 ka cal BP; Monge Soares et al., 2012; Martins, 2014) it is likely that these tracks have a depositional age of, at least, ca. 45e43 ka (MIS 3).

Fred


A Corvidichnus odemirensis from Aivados Sul beach section
C Buboichnus vicentinus trampled area interpreted as a predation/feeding trace;

scale is 10 cm.