Reduced Inner Toe Theropod Trackways Fro

8/17/2019 Reduced Inner Toe Theropod Trackways Fro

http://slidepdf.com/reader/full/reduced-inner-toe-theropod-trackways-fro 1/2

REDUCED INNER TOE THEROPOD TRACKWAYS

FROM EL MOLINO FORMATION (MAASTRICHTHIAN)

AT TORO TORO (BOLIVIA)

Sebastián Apesteguía1,2

, Silvina de Valais1, Christian A. Meyer

3, Giovanni Ríos

Cordero4

y Omar Medina5

1 Departamento de Paleontología. Fundación Patagónica de Ciencias Naturales, MuseoPatagónico de Ciencias Naturales, General Roca, Río Negro, ARGENTINA

[email protected] Área de Paleontología. Fundación de Historia Natural 'Félix de Azara', Dto. de Ciencias

Naturales y Antropología, CEBBAD, Univ.Maimónides, Buenos Aires, ARGENTINA3 Naturhistorisches Museum Basel, Augustinergasse 2, Postfach 1048, CH 4001 Basel4 Club Paleontológico Boliviano “FosilBol”, campus de Ciencias Puras, Universidad Mayorde San Andrés, La Paz, Bolivia. [email protected] SOCIUPA, Sociedad Universitaria Paleontológica de Sucre, Bolivia.

The Toro Toro tracksite reveals long sauropod, theropod, and ornithischiantrackways on Late Cretaceous limestones from the Lower Member of the El MolinoFormation (Middle Maastrichtian), deposited in a lacustrine environment, also related toshallow marine conditions. The rocks outcrop at the left margin of the Toro Toro river,

before joning the Mayu Mayu river, in the Toro Toro National Park, Bolivia. It is one of thefew globally known Latest Cretaceous dinosaur tracksites. Some of the observed theropodtrackways belong to a taxon whose inner toe is reduced in length to bear a distal bump. Thesame morphology was recognised in three different trackways and an isolated track, all ofthem in the same area and showing both left and right specimens, accounting for a total ofnine footprints produced by a bipedal trackmaker that left tridactyl footprints, notablyasymmetric respect to the central axis of the digit III impression, with no hallux preserved,most of the cases with poor to moderated quality of preservation. The most complete tracksshow a peculiar morphology, with complete digits III and IV impressions and anincomplete digit II. Considering that one of the specimens completely lacks the whole digitII and the inward sector of the sole impression, it is possible to conclude a trend to afunctional didactily. Length of individual tracks ranges from 16.4 cm to 28.8 cmincomplete (average of 22 cm), and width ranges from 7.5 cm to 20 cm (average 15.9 cm),

being the length:width ratio 1.4. The impression of digit III is the longest, commonly bearing a large claw mark, while the digit IV is relatively shorter and with a smaller clawmark. Phalangeal pads are not clearly impressed. The digit II, the more peculiar impression,only preserves the first phalangeal pad, that reach only 30 mm. This contrasts with digits IV(10.1 cm) and III (13.8 cm), with an average angle between the impression of digits II-III of16º, between digits III-IV of 17.8º, and a total divarication angle of 32.2º. It is worth to notethat in the more complete specimens, the metatarsal pads are very wide in the sector thatcontact digits, and the proximal ends of the digit impressions are separated each other,

providing a wider support. The preserved morphology is coincident with the pedal structureknown for a group of maniraptoran theropods formed by both troodontids anddromaeosaurids. However, differing from the presented evidence, the available

8/17/2019 Reduced Inner Toe Theropod Trackways Fro

http://slidepdf.com/reader/full/reduced-inner-toe-theropod-trackways-fro 2/2

reconstructions are represented as having the inner toe completely out of the ground

contact.Christian A. Meyer

Kommentar [1]: these must be

dromaeosaurid footprints, but be aware, that

they are preserved on a cliff, tectonical

movement can produce a lateral shearing an

then you think it is a "two" toed form. As it i

the case in many theropod tracks in Cal

Orck'O....

Reduced Inner Toe Theropod Trackways Fro

Documents

Transcript of Reduced Inner Toe Theropod Trackways Fro