Uvaichnites riojana Díaz-Martínez, Hernández, García Fernández, Murelaga, and Pérez-Lorente, 2012

Díaz-Martínez, Ignacio, Suarez-Hernando, Oier, Martínez-García, Blanca María, Larrasoaña, Juan Cruz & Murelaga, Xabier, 2016, First bird footprints from the lower Miocene Lerín Formation, Ebro Basin, Spain, Palaeontologia Electronica 12 (3), pp. 1-15 : 6-7

Uvaichnites riojana Díaz-Martínez, Hernández, García Fernández, Murelaga, and Pérez-Lorente, 2012

Figures 2.1-4, 3.1-3

Material. AG1-1, AG1-2, AG1-3, AG2-1.1, AG2- 1.2, AG3-1.1, AG3-1.2, AG3-2, AG3-3, AG3-4, AG4-1, and AG4-2.

Horizon and Locality. Lerín Formation of Agenian age (lower Miocene), Aguilares, Comunidad de Bardenas Reales , Navarra .

Description. Tridactyl, leptodactyl (slender digits), mesaxonic and unwebbed footprints with forwardly directed digit impressions. They are very large to enormous (see parameters of the ichnotaxobases in Díaz-Martínez et al., 2011, table 5) from 120 mm to 140 mm (average 130 mm) long. The footprints are wider than long, wide from 156 mm to 190 mm (average 170 mm). The central digit III impression is the longest (average 95 mm). Digit II is shallower and smaller than IV (average 57 mm and 76 mm, respectively). The digit divarication between digits II and IV is large and varies from 116º to 150º (average 131º). The footprints have angular asymmetry, average digit divarication between digits II and III is 62º less than between III and IV which is 70º.

Digital pad impressions are recognizable in well-preserved footprints (AG1-1, AG1-2; Figure 3.1-3 ), digits II, III, and IV (2, 3, 2, respectively). They are often only slightly visible, although there are very clear bumps on the sole of the footprints marking the lateral outline of the pads (e.g., AG1- 1). Digit impressions are slender and the proximal ends are not in contact with each other, even though they are sometimes very close to the central pad impression. The proximal part of digit III usually start more forward than digits II and IV proximal surface. The central pad impression is as long as wide average (25 mm x 25 mm). The best preserved one, footprint AG1-1, presents a wide proximal surface and a narrower distal part. In some tracks (AG1-1, AG1-2, AG4-1) very well-preserved claw marks have been identified (more than 1 cm long). Claw marks are narrower than the digit impressions and present a very acuminate distal end ( Figure. 4.1-3 ). The digit III claw mark is straight and digit claw marks II and IV are laterally curved. No evidence of webbed toes is preserved.

The pace length of two pairs of footprints (AG2-1 and AG3-1) is 400 mm and 470 mm, respectively.

Figures

FIGURE 2. Photographs and sketches of the blocks of the Aguilares bird footprints. 1, AG1 block; 2, AG2 block; 3, AG3 block; 4, AG4 block.

FIGURE 3.1, Picture; 2, false-color depth map of the photogrammetric model; 3, contour lines map with 0.5 mm of equidistance of AG1-1 footprint. 4, Picture, 5, false-color depth map of the photogrammetric model; 6, contour lines map with 0.5 mm of equidistance of Uvaichnites riojana holotype.

FIGURE 4. Detail of claw marks of Aguilares Uvaichnites riojana. 1, Digit III of AG1-1; 2, digit III of AG1-2; 3, digit IV of AG1-1; 4, Extant crane foot Grus leucogeranus. White arrows indicate the foot claws.