TABLE 1. Measurements of the bird footprints of Lerín Formation. Abbreviations: FL, footprint length; FW, footprint width; cpLxW, central pad length and width; II, digit II length; III, digit III length; IV, digit IV length; II^III, angle between digits II and III; III^IV, angle between digits III and IV; II^IV, angle between digits II and IV; PL, pace length. All parameters are given and compared in millimeters, except for II^III, III^IV, and II^IV, which are in degrees.
| FL | FW | cpLxW | II | III | IV | II^III | III^IV | II^IV | PL | |
| AG1-1 | 136 | 174 | 30x20 | 62 | 94 | 80 | 60 | 66 | 126 | - |
| AG1-2 | 130 | - | 25x- | - | 98 | 80 | - | 70 | - | - |
| AG1-3 | - | - | - | - | - | - | - | - | - | - |
| AG2-1.1 | 121 | 164 | 25x25 | 58 | 90 | 70 | 68 | 70 | 138 | - |
| AG2-1.2 | 120 | - | 25x20 | - | 90 | 78 | - | 76 | - | 400 |
| AG3-1.1 | 123 | 157 | 24x28 | 50 | 92 | 72 | 58 | 58 | 116 | - |
| AG3-1.2 | 124 | - | - | 44 | 86 | - | 58 | - | - | 470 |
| AG3-2 | 154 | 178 | 28x30 | 55 | 112 | 78 | 74 | 76 | 150 | - |
| AG3-3 | 140 | - | 25x26 | 66 | 95 | - | 63 | 63 | 126 | - |
| AG3-4 | 124 | 156 | 20x22 | 55 | 94 | 70 | 61 | 67 | 128 | - |
| AG4-1 | 125 | 190 | 20x25 | 65 | 92 | 82 | 58 | 78 | 136 | - |
| AG4-2 | - | 172 | - | 60 | 100 | - | 59 | 72 | 131 | - |
| Mean | 130 | 170 | 25x25 | 57 | 95 | 76 | 62 | 70 | 131 | - |
TABLE 2. Avian fossil record from the early Miocene in the Iberian Peninsula. All the information is extracted from Sánchez-Marco (1999, 2006), Mlíkovský (2002), Grellet-Tinner et al. (2012), and Díaz-Martínez et al. (2015). Only the most recent taxonomic/ichnotaxonomic determination is considered.
| Taxon/ichnotaxon | Zone | Locality (province) | Reference |
| Koreanaornis isp. | MN 1- MN 3 | Los Arcos (Navarra) | Díaz-Martínez et al. (2015) |
| Aves indet. | MN 2 | Navarrete (Teruel) | Adrover (1975) |
| Gruipeda cf. máxima | MN 2 | Cenicero (La Rioja) | Díaz-Martínez et al. (2011) |
| Uvaichnites riojana | MN 2 | Cenicero (La Rioja) | Díaz-Martínez et al. (2012) |
| Koreanaornis isp. | MN 2 | Cenicero (La Rioja) | Díaz-Martínez et al. (2015) |
| Uvaichnites riojana | MN 2 | Aguilares (Navarra) | In this work |
| Plesiocathartes? gaillardi | MN 3 | El Fallol (Barcelona) | Crusafont and Villalta (1955) |
| Phoenicopteridae indet. | MN 3 | Bardenas Reales (Navarra) | Murelaga (2000) |
| Phoenicopteridae indet. | MN 3 | Bardenas Reales (Navarra) | Grellet-Tinner et al. (2012) |
| Palaeortyx edwardsi | MN 4 | Can Mas (Barcelona) | Villalta (1963) |
| Miophasianus altus | MN 4 | Can Mas (Barcelona) | Sánchez-Marco (2006) |
| Aves indet. | MN 4 | Alto de Ballester (Teruel) | Sánchez-Marco (1999) |
| Aves indet. | MN 4 | La Retama (Cuenca) | Sánchez-Marco (1999) |
| Aves indet. | MN 4 | Estación Imperial (Madrid) | Sánchez-Marco (1999) |
| Aves indet. | MN 4 | La Artesilla (Zaragoza) | Sánchez-Marco (1999) |
| Miophasianus sp. | MN 4 | Córcoles (Guadalajara) | Alférez et al. (1982) |
| Aves indet. | MN 4 | Els Casots (Barcelona) | Sánchez-Marco (1999) |
| Large bird tracks | MN 4- MN6 | Salinas de Añana (Álava) | Antón et al. (1993) |
| Small bird tracks | MN 4- MN6 | Salinas de Añana (Álava) | Antón et al. (1993) |
