Huellas de mamíferos en Álava (Mioceno) by Ignacio Díaz

Carnivore Trackways from the Miocene Site of Salinas de Anana ˜ (Alava, Spain) Mauricio Anton Departamento de Paleobiolog´ıa, Museo Nacional de Ciencias Naturales, Madrid, Spain

Gregorio López and Robert Santamaria Departament de Geologia (Paleontologia), Facultat de Ciències, Universitat Autònoma de Barcelona, Spain

A fossil tracksite of Lower Miocene age discovered near Salinas de Anana, ˜ Alava (Spain), has rendered an exceptionally wellpreserved assemblage of vertebrate ichnites. The site shows a high proportion of carnivore tracks (3 out of 5 mammal ichnospecies) and a high number of individual trackways (15), some including over 50 consecutive footprints. The carnivore ichnites are classified as Felipeda lynxi Panin & Avram, 1962, Felipeda parvula ichnosp. nov. and Canipeda longigriffa Panin & Avram, 1962, and they are attributed to a felid, an undetermined small aeluroid, and a herpestid, respectively. The long trackways allow determination of gaits, which include lateral sequence walks and diagonal sequence trots, and of speed, which ranges from 0.4 to 1.4 m/s. Froude numbers range between 0.1 and 0.8, agreeing with gait interpretations and speed calculations. The felid trackways provide the first known evidence of group traveling in fossil cats. The herpestid footprints show modern-grade adaptations for terrestrial locomotion and digging. Keywords Mammalia, ichnites, trackways, carnivores, cats, mongoose, Miocene, Spain

INTRODUCTION A lower Miocene tracksite discovered near Salinas de A˜nana (Alava, Spain) (Laumen, 1989; Ant´on et al., 1993 and 1999) shows abundant, exceptionally preserved vertebrate trackways (Fig. 1). About 60 square meters of the site have been excavated until now, yielding about 700 footprints, many of them in clear trackways (Figs. 2 and 3). The site includes at least 15 carnivore trackways, some of exceptional length with over 50 consecutive footprints, and with an exquisite preservation of morphological detail. Apart from the carnivore trails, there is another clear mammal trackway (marked

Address correspondence to Mauricio Anton, Departamento de Paleobiolog´ıa, Museo Nacional de Ciencias Naturales, C/Jose Gutierrez Abascal 2, Madrid, 28006, Spain.

“U” in Fig. 2) corresponding to a small ruminant, although there are many footprints of a small artiodactyl that cannot be easily grouped into individual trackways and are attributed to a member of the family Cainotheridae (Antón et al., 1993 and 1999). This abundance of carnivore trackways is remarkable, considering that carnivore ichnites are rare in the fossil record, so that even in exceptional tracksites with long trackways of other mammals only isolated footprints of carnivores are usually found (Robertson and Sternberg, 1942; Alf, 1959; Scrivner and Bottjer, 1986; Pérez-Lorente et al., 1999). Also, and in the rare cases where trackways are available, preservation of morphological detail is usually poor (Alf, 1966; Leakey and Harris, 1987). The tracks from Salinas allow the most detailed study to date of the locomotion of Miocene carnivores, as well as morphological comparisons that reveal the phylogenetic affinities of the trackmakers. In addition to the mammalian trackways, the site preserves two bird ichnospecies. All the tracks are preserved in a finegrained limestone laid on an ancient lakeshore. The remarkable detail of the footprints suggests that they were produced near the shoreline, within the strandline zone (Cohen et al., 1991, 1993). In this zone the water content of the sediment allows excellent preservation of small animal footprints, but high bioturbation tends to destroy them quickly, so burial must occur within days of ichnite production to allow preservation. These data point to a lacustrine basin subject to sudden, seasonal floods, one of which buried the tracks and led to their preservation. This conclusion is also supported by detailed sedimentologic studies and regional palaeogeographic reconstructions on our studied area (Dreikluft, 1996; Laumen, 1989), that consistently report the presence of braided rivers and ephemeral floodplain lakes during the Oligocene and lowermost Miocene in this region. The Salinas de Añana section that includes the track-bearing beds is sedimentologically characterized by an alternation of sandstones and silt beds with load casts related to the high original

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FIG. 1.

Geographic situation of the Salinas de A˜nana tracksite.

water content of the sediment, some fine-grained limestones with charophytes, and Pulmonata gastropods related to lake facies. This stratigraphic sequence clearly corresponds to the distal part of a fluvial system close to some lakes (facies association FA VII of Dreikluft, 1996). The sediments are dated as Burdigalian (= Aragonian) in previous geological studies (IGME, 1978; Dreikluft, 1996) and the ichnites are consistent with this age (Ant´on et al., 1993, 1999). The mongoose tracks are significant because herpestid fossils are first recorded in Europe by MN4, in the early Aragonian (Schmidt-Kittler, 1987; Ginsburg, 1990). The abundant tracks of a minute artiodactyl attributed to the family Cainotheridae (Ant´on et al., 1993, 1999) are also important because this family is last recorded in biochronological zone MN 6 (de Bruijn et al., 1992). According to the biochronological scheme proposed by Mein (1979), the above data date the site between the beginning of MN4 (20 Ma) and the end of MN 6 (15 Ma). MATERIALS AND METHODS The tracks were traced on sheets of Perspex directly over the sediment. All 15 carnivore trackways were measured, but in this paper we only present analyses of seven, which display the best preservation of locomotor information, and are representative of the rest. Footprint dimensions, stride length and glenoacetabular distance were measured directly on the trackways, following the methodology of Leonardi (1987). Glenoacetabular distance (Fig. 4) is defined as the distance between two points, which are the theoretical projection on the ground of the

shoulder and hip joints, approximating the living animal’s body length. Methods for estimating glenoacetabular distance vary according to the gait of the trackmaker. In trackways indicating a trot or a walk in diagonal sequence, the distance measured is the segment above the midline that unites the intersection points between the midline and two lines: the one joining the reference points of the manus and the one joining the reference points of the pes (Leonardi, 1987, pl.8-c). An alternative, slightly different method for estimating glenoacetabular length is to measure the distance between the midpoint of the segment uniting the two consecutive hind footprints and the midpoint of the segment joining the next pair of consecutive fore footprints (Moratalla et al., 1989). This method yielded more consistent estimates in narrow trackways, so we favored it when measuring the Salinas trails that corresponded to diagonal sequence gaits (Fig. 5, left and center). In the case of trackways corresponding to a walk in lateral sequence, the distance measured is the length of the segment of the midline that joins the two following points: 1, the projection of the reference point of the more advanced forefoot and 2, the intersection of the midline with the line that joins the reference point of the two hind feet of the other two sets (Fig. 5, right). As stressed by Leonardi (1987, p. 48), there are no absolute rules to determine which hypothesis to choose, so the option can only be taken after careful examination of each trackway. In the case of the Salinas tracks analyzed in this study, the great length of most of the trackways facilitated the determination of gait, because many successive series can be measured to test the consistency of the hypotheses.

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FIG. 2. Trajectories of the main trackways. Tracks named R are Felipeda lynxi, K is for Felipeda parvula and I for Canipeda longigriffa, U is a small artiodactyle and A are bird tracks. Numerous tracks of a very small artiodactyle cross the site in all directions, but have been omitted in this drawing to avoid confusion. Note parallel felid trackways R6, R7, R9 and R10.

Determining the gait was done through examination of the trackway configuration using the methodology of Halfpenny (1986) and Leonardi (1987). The speed of the trackmakers was calculated using the formula of Alexander, V = 0.25 × g 0.6 × λ1.67 × h−1.17 (Alexander, 1976). This method in turn requires an estimate of limb height (femur plus tibia plus metatarsal plus 9%) for each trackmaker. To obtain such estimates, we reviewed the body proportions of comparable carnivores both living and extinct. Using photographs of living animals and published figures for hind-limb bone lengths (Walker, 1985) and for footprint length (Stuart and Stuart, 1994), we calculated the following ratios for extant carnivores:

1) Ratio of limb height to footprint length. 2) Ratio of limb height to glenoacetabular length. The first ratio (Table 1) was calculated from published data of five species of extant African small to medium-sized aeluroids: serval cat, Felis serval (Schreber, 1776); leopard, Panthera pardus (Linnaeus, 1758), common genet, Genetta genetta (Linnaeus, 1758); african civet, Civettictis civetta (Schreber, 1776); and egyptian mongoose, Herpestes ichneumon (Linnaeus, 1758). The latter species is regrettably the only herpestid for which we found data on both footprint size and skeletal measurements to match, but since Herpestes (Illiger, 1811) is a rather generalized herpestid and likely a reasonable model for

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FIG. 3. Photograph of a section of the Salinas tracksite. On the left side there is a trackway of the ichnospecies Felipeda lynxi and tracks of a small ungulate. Another Felipeda lynxi trail crosses from the top of the picture toward the right bottom corner, and broadly parallel below it runs a trail of Felipeda parvula. A trackway of Canipeda longigriffa (mongoose tracks) runs across the right bottom corner.

the more primitive, early members of the family, we consider that the data provide a valid approximation. In addition, our review of other herpestids, not included here because only part of the set of measurements could be taken on each species, indicates a broad similarity in proportions within the family. Although the leopard is considerably larger than the other carnivores in the list, it was included because its short-limbed proportions are more likely to resemble those of the lower Miocene felids than the extremely long-limbed, but more con-

veniently sized, serval cat (Ginsburg, 1961a). The results of this review show small to medium aeluroids with retractable claws averaging 9.23 (average of the values for serval, leopard, civet and genet shown in Table 1), while African Herpestes, displays a much lower value at 5.8. It thus appears that herpestids have longer footprints (excluding the claws) relative to hind limb dimensions. We estimated the height of the limb of the Salinas carnivores, which have retractable claws using the average value for modern cats and viverrins (9.23),

FIG. 4. Outline drawing traced from a photograph of a banded mongoose, showing the positions of the main limb bones as inferred from the situation of relevant points of the external anatomy (Done et al., 1999). Vertical broken lines indicate the projections on the ground level of the glenoid of the scapula and acetabulum of the pelvis, which in turn define the glenoacetabular distance (a-b).

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FIG. 5. Diagrams of carnivore trackways recognized at Salinas. Left, K3 (Felipeda parvula); center, I1 (Canipeda longigriffa); right, R2 (Felipeda lynxi). Hind footprints are filled in black. Segment a-b = glenoacetabular distance; M, midline; Sf, step of forelimb; Sh, step of hind limb; St, Stride. Scale bars = 5 cms.

while for the Salinas herpestid we used the value of modern Herpestes. The second ratio was calculated from the analysis of photographs of living animals in lateral view (Fig. 4). To estimate the relative lengths of the hind-limb bones and the glenoacetabular distance, we inferred the position of the articulations using

reference points in the external surface of the body, as defined by Done et al. (1997). After reviewing hundreds of photographs, we found that only a few of them showed the animals in side view with body proportions clear enough and with their entire limbs visible. We analyzed 11 photographs in side view corresponding to 7 species of small aeluroid carnivores that were considered

TABLE 1 Average footprint length (l), Hind-limb height, equaling femur + tibia + metatarsus + 9% (h) and h/l ratio in five extant African aeluroid carnivores. Footprint data from Stuart and Stuart (1994), and limb bone data from Walker (1985).

Average footprint length (l) Limb height (h) h/l

Serval

Leopard

Genet

Civet

Mongoose

45 495 11

90 670 7.4

21 237 11.3

48 344 7.2

42 245 5.8

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acceptable analogues of the Salinas trackmakers because of their digitigrade stance and generalized body proportions. The species analyzed were: domestic cat, Felis catus (Linnaeus, 1758) (n = 2); serval cat (n = 1); common genet (n = 3); African civet (n = 2); Asian ground civet, Viverra tungalunga (n = 1); white tailed mongoose, Ichneumia albicaudia (Cuvier, 1788) (n = 1); and banded mongoose, Mungos mungo (Gmelin, 1788) (n = 1). Our review shows that felids, viverrids, and herpestids are rather homogenous, averaging a ratio of 0.93 with a minimum of 0.85 and a maximum of 1,03. Variation within the sample of one species was comparable to that observed between species, which makes us confident that the ratio is fairly constant among small digitigrade members of the Aeluroidea. The average ratio of 0.93 is thus used for the estimates of limb height offered in Table 2. The average ratios obtained for modern species were used to estimate limb height from known track dimensions (footprint length and glenoacetabular length) in the Salinas trackways. Finally, we averaged the values obtained with both methods, so that the possible biases in each one are compensated (Table 2). A review of the body proportions of small and medium sized lower Miocene aeluroid carnivores shows that they generally resemble their extant relatives. Larger members of the Aeluroidea tend to evolve more specialized body proportions, some with exceedingly robust, short limbs, others with very elongated limbs and in some cases shortened backs, but the smaller species are in general more conservative (Ewer, 1973). Fossil evidence indicates that lowermost Miocene cats had relatively short limbs, resembling the more scansorial among extant members of the cat family. We estimated the Froude number using the method of Alexander (1991). This number (v2 /gl) relates speed to limb height,

illustrating the relative effort of an animal during locomotion. As the Froude number increases, that is, as the speed increases relative to the animal’s limb-height, it becomes more energetically efficient for animals to “change gears” and turn from walk to trot and from trot to gallop. Ideally, the Froude number and the speed estimations should fit with the gait reconstruction as inferred from the trackway measurements. Error Margins The incorporation of average values of limb height into the speed calculations introduces a certain margin of error. For instance, if we would estimate the limb height of trackway R2 (Table 2) using the ratio of footprint length to limb height of the leopard (7.4), instead of the average value for carnivores with retractable claws, then the speed estimate would change from 0.76 m/s to 0.87 m/s, and the Froude number would be 0.23 instead of 0.16. But, if we had used the ratio of the genet (11.3) then the speed would have been 0.66 m/s and the Froude number would become 0.66. In fact, the limb height estimates based on footprint length ratios are consistently higher than estimates based on glenoacetabular length in the Felipeda lynxi Panin & Avram, 1962 trackways, while they are more similar in the other species, making us suspect that the trackmaker might have been robust and short-limbed like the extant leopard, so it would be tempting to drop the averages and use that ratio instead. But we have preferred to use ratios as uniform as possible for the trackmakers with retractable claws, rather than having to choose in a more or less arbitrary way for each particular case. Thus, the speed estimates for R2 could be expressed as 0.76 m/s ± 0.1 m/s. Such an error margin seems tolerable because both the speed estimate and the Froude number in each case would still be broadly in accordance with the gait inferences and with other parameters of the trackway, such as footprint length-to-stride ratios.

TABLE 2 Measurements and estimated limb height, speed and Froude numbers in representative carnivore trackways from Salinas. See Fig. 2 for trackway keys. Trackway Footprint length (mm) Gleno acetabular distance (mm) Stride (mm) = λ Limb height (mm) = h

Speed (m/s) Froude number Gait

Average n Extremes Average Extremes Average Ratio 1 Results 1 Ratio 2 Results 2 Average

48 36 394/440 420 486/570 520 Fl × 9.23 443 Gd × 0.93 391 417 0.731 0.131 Walk

44 24 368/388 380 470/518 500 Fl × 9.23 406 Gd × 0.93 353 380 0.763 0.156 Walk

51 10 465/482 474 495/577 540 Fl × 9.23 470 Gd × 0.93 441 456 0.701 0.110 Walk

48 26 360/397 381 672/676 735 Fl × 9.23 443 Gd × 0.939 354 399 1.371 0.481 Trot

42 58 245/292 269 450/590 520 Fl × 5.8 244 Gd × 0.93 250 247 1.348 0.751 Trot

194/234 220 380/530 440 Fl × 9.23 203 Gd × 0.93 205 204 1.276 0.814 Trot

223 250/233 240 Fl × 9.23 212 Gd × 0.93 223 218 0.429 0.086 Walk

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Classification In morphological terms, the carnivore tracks from Salinas are similar enough to previously described ichnites from other sites as to be included in already existing ichnogenera, although in all cases the ichnites from Salinas display a much better preservation of detail, and the samples are much larger. In some cases there are reasons to think that the ichnites were not produced by animals belonging to the same genus or even to the same family as the presumed trackmakers of the tracks that were the basis of morphologically related ichnogenera, but such problems are intrinsic to the method of ichnological parataxonomy. When studying well-preserved ichnites that can be attributed with reasonable confidence to extant families of mammals, as is the case with the Salinas tracks, it may be legitimate to object to the use of a parataxonomy, which may add more confusion than clarity to the interpretation of the fossil evidence. While many previous studies of Neogene mammal tracksites have classified the respective ichnites in ichnogenera and ichnospecies (Lockley and Meyer, 2000 and references therein), the opposite approach is exemplified in the study of vertebrate tracks from the African Pliocene tracksite of Laetoli (Leakey and Harris, 1987). Earlier studies on Salinas de A˜nana footprints were preliminary in adopting an informal nomenclature of the ichnites (Ant´on et al., 1993 and 1999). In the present study, and for the sake of easier reference, we have adopted the generally accepted criteria for naming ichnites, assigning the Salinas carnivore tracks to two different ichnogenera. The exquisite preservation of detail in the Salinas tracks warrants assignment down to the ichnospecies level, according to the criteria specified by Leonardi (1987). Besides the ichnotaxonomic classification of the tracks, we attempt the attribution to known fossil taxa of the lowest possible taxonomic level through a review of the fossil record of the Carnivora in the Miocene of Western Europe. Reconstruction Putting together the information on track measurements, gait, inferred body length and limb height, and hypothetical attribution of the trackways to fossil taxa, we attempt a reconstruction of the trackmakers. The reconstructed animal is shown on top of a selected trackway segment, moving in the corresponding gait. The reconstruction is drawn to the same scale as the tracks, allowing us to check if the inferred body proportions and gait are consistent with the track measurements. An incorrect inference might result in an impossibly or incoherently proportioned animal. The classic photographic sequences of Muybridge (1957) were especially useful for checking the relationship between gait and limb posture in walking and trotting carnivores SYSTEMATIC ICHNOLOGY Ichnogenus Felipeda Panin and Avram, 1962 Felipeda lynxi Panin and Avram, 1962 Figs. 3, 5, 6, 7,8,12 and 13, Table 2

FIG. 6. Photograph of a section of a trackway of Felipeda lynxi. Notice a tail drag mark, which coincides with the change in direction of the trail. Parallel to this track to the right is a Felipeda parvula trackway.

* 1962 Felipeda lynxi n. gen., n. sp.; Panin and Avram, p. 461, làm. II, fig. 15. v 1993 Carn´ıvoro grande; Antón, López and Santamar´ıa p. 2324, figs. 2a and 2b. v 1999 Félido R3; Antón, López and Santamar´ıa p. 153, làm. I, figs. 1 and 2. Number of tracks: There are ten trackways attributed to this ichnospecies, which cross the excavated area in all directions (Figs. 2, 3, 6 and 7).

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2. A greater asymmetry of some of the footprints, pointing to a more supinated posture of the feet. In this trait, the Salinas trackmaker resembles some living arboreal viverrids such as Nandinia binotata (Reinhard, 1830), which also produces asymmetrical footprints (Liebenberg, 1992; Taylor, 1970, 1974).

FIG. 7.

Close up photograph of two footprints of Felipeda lynxi.

Description: These tracks are indistinguishable in size and morphology from those originally described as Felipeda lynxi by Panin and Avram (1962), from the lower Miocene of the Vrancea region in Romania, although the preservation of the Salinas tracks is much more detailed and of course the sample size is incomparably larger. The footprints average about 50 mm in length and 40 mm in width, they are paraxonic, with four digits, fused interdigital pads, and retracted claws (Ant´on et al., 1993 and 1999); the interdigital pad has a slight anterior indentation and double posterior indentation typical of extant aeluroid footprints (Fig. 8a). Discussion: These footprints correspond to an animal about the size of an extant Spanish lynx, Lynx pardinus (Temminck, 1827), and generally resemble modern felid tracks, although there are several morphological differences with the latter, including: 1. A relatively longer interdigital pad, meaning a less digitigrade stance; this difference is due to the reduction, in modern cats, of interdigital pads 2 and 4, still well developed and projecting posterior from the main pad in the Salinas tracks (Fig. 8a).

On purely morphological grounds, these tracks could correspond to either a viverrid or an early hyaenid. The possibility that they correspond to a viverrid is currently rejected on the basis of size. The only viverrids with retractable claws known to have inhabited Europe are members of the subfamily Viverrinae, such as genets or civets. No fossil or living genet ever attained such large size as the species that left the larger carnivore tracks from Salinas, and Miocene civets were also relatively small animals (Ginsburg, 1961). A size problem also applies for the fossil hyaenids. The earliest members of the hyaenid family retained some degree of claw retractability, which was lost in the course of evolution, so a hyaenid of early Miocene age could possibly make tracks morphologically similar to these ones. However, fossil hyenids of that age were far smaller than the lynx-sized animal that left these tracks, and their skeletons betray a more complete adaptation to terrestrial locomotion than that seen in early cats (Beaumont and Mein, 1972; Hunt and Solounias, 1991; Werdelin and Solounias, 1991) so we can expect that their footprints would resemble more those of cursorial carnivores, displaying more reduced interdigital pads. On the other hand, footprint morphology of the Salinas trackmaker matches skeletal features in the limbs of Pseudaelurus Gervais, 1850, the felid genus typical of the early Miocene, which retained several arboreal adaptations from some viverridlike ancestor (Ginsburg, 1961a, b). The feet of Pseudaelurus were less fully digitigrade than those of modern felids, and several features of the limb bones indicate a greater ability to rotate the feet. Felid footprints of later age, such as those from the Hemphillian of Death Valley in California, described as several species of Bestiopeda (Felipeda) by Scrivner and Bottjer (1986), show a modern pattern, with interdigital pads 2 and 4 reduced and pressed tightly against pad 3, as in living cats. All these data point to a small species of Pseudaelurus as the probable trackmaker. The estimated dimensions of the limbs of the Salinas trackmaker are in between those of the wildcat-sized Psedaelurus turnauensis and the lynx-sized P. lorteti. There is considerable size variation within, and even overlap between, the two species, so the Salinas tracks could correspond either to a large variety of the small species or a small-bodied population of the larger taxon. (Viret, 1951; Heizmann, 1973; Ginsburg et al., 1981; Ginsburg, 1999). Felipeda parvula n. ichnosp. Figs. 3, 5, 6, 8, 9 and 12, Table 2 v 1993 Carn´ıvoro pequeño; Antón, López and Santamar´ıa p. 24, fig. 2h.

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FIG. 8. Pad patterns of the Salinas carnivores with reconstruction of the autopods (top row) compared to those of living carnivores (bottom row). a) The larger felid from Salinas, Felipeda lynxi (i) has a longer interdigital pad compared to the living serval (ii). 2, 3 and 4: interdigital pad numbers. b) The herpestid footprints from Salinas, Canipeda longigriffa (i) are very similar to those of the living gray mongoose (ii). c) The undetermined small aeluroid from Salinas, Felipeda parvula (i) has a shorter and more simplified interdigital pad than the living genet (ii).

Holotype: Footprint Number MCNA 1240-KP1 (Fig. 9), which is preserved as a resin cast at the Museo de Ciencias Naturales de Alava (Vitoria, Spain), and provisionally exposed at the town hall of Salinas de Añana. Rubber and sand beds in the footprint site at Salinas de Añana protect the original specimen. Hypodigm: is the set of ichnites of trackway KP (Fig. 9). This set is preserved in the same resin cast (MCNA 1240) as the holotype and is also housed at Museo de Ciencias Naturales de Alava (Vitoria, Spain). Locality: Lower Miocene (Burdigalian, = Aragonian) sequence at Salinas de Añana, Alava (Spain). Diagnosis: Paraxonic tracks, averaging 23 mm in length, and 24 mm in width, with four toe pads and no claw marks, simplified, sub-triangular, and wider than long interdigital pad, made up of three fused pads, with slight anterior indentation. Differs from Felipeda lynxi in being absolutely smaller and in having a relatively smaller, shorter interdigital pad, with pads 2 and 5 projecting less posteriorly (Figs. 8c and 9). Derivatio Nominis: parvula meaning small, for the minute size of the ichnites. Number of tracks: There are four trackways of this small carnivore, one of which (named KP) is a natural cast; the original corresponding trackway was never found in the site.

Discussion: Ichnites are about the size of a modern genet (Figs. 3, 6 and 9). They resemble the footprints of living viverrines and cats (Ant´on et al., 1993 and 1999), according to data of Stuart and Stuart (1994), but a third possibility is that they correspond to an early hyenid. Living hyenids are large carnivores with non-retractile claws, but the early Miocene hyenids were small animals resembling modern viverrines, with primitively long bodies and partly retractile claws. These traits are evident in the Salinas tracks, which lack claw marks and where footprint length is about one tenth of the glenoacetabular length, implying small feet and a long body (Pilgrim, 1931; Hunt and Solounias, 1991). The difficulties in attributing these tracks at the family level can be summarized as follows: 1. The tracks match the size and body proportions of extant and fossil genets (Fig. 8c), but the reduction of the interdigital pads suggests a more evolved, cursorial animal than any living genet. The known limb anatomy of Semigenetta repelini (Helbing, 1927), a genet of approximately the same geological age as the Salinas ichnites, is remarkably similar to that of extant genets and indicates that the footprints would also be similar. Other species of the genus Semigenetta are known from partial remains, all

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indicating a gait and structure similar to that of modern genets (Ginsburg, 1999). 2. The configuration of the footpads matches that of some living felids, and some species of Miocene cats such as Pseudaelurus turnauensis are almost as small as this trackmaker. The foot anatomy of those small cats is not well known and it is possible that they were more terrestrially adapted than their larger relatives, and thus might have produced footprints like these. 3. The tracks fit well with the osteology of such ictitherine hyaenids as Plioviverrops Kretzoi and Protictitherium, which include species of the right size and age (de Beaumont and Mein,1972) but ictitherines are an extinct group and we can only make inferences about their footpad structure. In brief, while the cursorial adaptations evidenced by the footpad reduction in these footprints may point to an early hyaenid as the possible trackmaker, a small felid appears just as feasible. Ichnogenus Canipeda Panin and Avram, 1962 Canipeda longigriffa Panin and Avram, 1962 Figs. 2, 3 and 11 * 1962 Canipeda longigrifa n. gen., n. sp.; Panin and Avram, p. 461–462, làm. II, fig. 16. v 1993 Carn´ıvoro mediano; Antón, López and Santamar´ıa p. 24, fig. 2c.

FIG. 9. Photograph of trackway KP of Felipeda parvula n. ichnosp. Holotype (MCNA 1240-KP1) and Hypodigm of the ichnospecies.

Number of tracks: There is one, very long trackway of this species (Figs. 2, 3 and 11). Description: Paraxonic tracks averaging 48 mm in length and 33 mm in width, with four parallel oriented digit prints; simplified, sub-trapezoidal, relatively large interdigital pad made up of three fused pads, with slight anterior indentation; claw marks indicating large, non retracted claws which are longer in the fore than in the hind feet (Ant´on et al., 1993 and 1999). Occasionally there may be a faint print of the claw of digit 1 (Figs. 8b and 10). Discussion: The tracks are indistinguishable in size and shape from a footprint described by Panin and Avram (1962) under the name Canipedia longigriffa. While adopting the generic and specific designations coined by those authors, we feel that the generic name is strongly misleading, because it unambiguously points to attribution of the tracks to a member of the canid family. Such an attribution was based on the observation of superficial similarities, but the large size of the interdigital pad relative to the toe pads, as well as the detailed morphology of the interdigital pad, clearly distinguish these tracks from true canid footprints, and indicate that they were produced by a mongoose, an attribution which also makes sense in biogeographic terms, as commented below. So, while adopting the original denomination for formal reasons, we want to emphasize that the attribution of both the Romanian and Spanish tracks to a herpestid appears to us unambiguous. The difference in length between the claws of the fore and hind feet evidenced in this trackway (Fig. 10) is normal in

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in the lower Miocene of Europe, and strengthen the case for a Palaearctic origin of the group (Petter, 1974). Another example of the presence of herpestid tracks in the early Miocene of Europe is a footprint from Romania, attributed to a canid and described as Canipeda longigriffa by Panin and Avram (1962). The footprints of canids differ strikingly from those of herpestids as commented above, and members of the family canidae evolved in North America and are unknown in Europe until the Turolian (Late Miocene) (Agust´ı and Ant´on, 2002).

FIG. 10. Close-up photograph realized on two footprints of Canipeda longigriffa. Top, left fore foot, bottom, left hind foot.

modern carnivores that have digging habits. The footprints (Fig. 8b) are remarkably similar in size and shape to those of the living Egyptian mongoose, Herpestes ichneumon, as clearly observed on data from Stuart and Stuart (1994). Herpestid footprints cannot be confused with those of any other aeluroid carnivore. They superficially resemble the tracks of hyenas because both have claw marks, but in the latter the toe pads are much more closely pressed to the interdigital pad, which in turn is proportionally much smaller than in herpestids. These are to our knowledge the first data on the foot morphology of Miocene herpestids, which hitherto were known only on the basis of teeth and fragmentary cranial material. The foot features displayed by the Salinas tracks seem to be derived traits among herpestids and aeluroids in general. According to Ewer (1973), the primitive herpestid foot morphology is retained in the living galidine Galidia elegans (Geoffroy), a semiarboreal mongoose from Madagascar, with fan-like splaying digits, short claws, and well-separated, non-reduced interdigital pads. Leptoplesictis, the only known herpestid genus from that age has a very primitive dentition, similar to that of Galidia (Petter, 1974), and such a primitive dentition might lead one to believe that lower Miocene herpestids would have a similarly primitive foot pattern. Contrary to such expectations, the Salinas ichnites, which very likely correspond to Leptoplesictis, show feet of modern grade, well adapted to terrestrial locomotion and digging. From a palaeobiogeographical point of view, these footprints confirm the presence of herpestids of basically modern grade

LOCOMOTION The configurations of the trackways (Fig. 5) correspond with symmetrical gaits, trots and walks in diagonal and lateral sequences (Halfpenny, 1986). The glenoacetabular length is fairly constant in the long trackways (Table 2) and this indicates that there was little or no dorsoventral flexion of the spine during locomotion, as is normal in walking and trotting carnivores (English, 1980). Stride length is small to moderate in all the trackways (Table 2), corresponding with the slow speeds of walk and trot. In three of the tracks, R6 (Felipeda lynxi) I1 (Canipeda longigriffa), and K3 (Felipeda parvula) the stride length approximates a dimension twice that of the estimated limb height, agreeing with the diagonal sequence-trotting gait indicated by trackway configuration. Froude numbers of the various trackways are low and consistent with the gaits inferred form trackway measurements, and once again the highest figures are those of the three trotting trackways, R6, K3 and I1. According to Alexander (1976) mammals change gaits from walk to trot or run at Froude numbers around 0.6, and while the figure for R8 is somewhat lower, those of I1and K3 are above that limit. All the studied trackways from Salinas yield Froude numbers well below the figure 2.6 given by Alexander (1991) for the transition to gallop in modern mammals. RECONSTRUCTION The reconstruction of the body outlines of the trackmakers drawn over the trackways allows us to test the consistency of our inferences about body proportions and gait (Fig. 12). Felipeda lynxi is reconstructed on the basis of the anatomy of the fossil felid genus Pseudaelurus; Felipeda parvula was drawn after the proportions of the fossil hyaenid genera Plioviverrops and Protictitherium. Canipeda longigriffa was drawn after the body proportions of modern Herpestes because the pos-cranial skeleton of Miocene herpestids is virtually unknown. The dental and mandibular remains of the fossil herpestid Leptoplesictis allow at least an estimate of body size, which was used as a guide for the reconstruction of Canipeda longigriffa. The consistency of the reconstructions with the measurements of the trackways is remarkable, and serves as an additional test for the gait inferences and taxonomic attributions. As commented above, the relationship between body proportions and footprint dimensions among the aeluroid carnivores with retractable claws displays similar variations across families, so

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FIG. 12. Reconstructions of three species of carnivore trackmakers from Salinas, drawn to the same scale relative to each other and to the trackway segments. Top, Felipeda lynxi, with a segment of trackway R1; center, Felipeda parvula, with a segment of trackway K3; bottom Canipeda longigriffa, with a segment of trackway I1. On each trackway segment, the footprints that correspond to the feet touching the ground in the reconstruction are shaded in black.

it remains feasible that Felipeda parvula could be reconstructed as a small cat. On the other hand, the relatively long, clawed feet of herpestids leave little doubt as to the identity of the Canipeda longigriffa tracks. A further step is to attempt a realistic restoration of the trackmakers. As shown for Felipeda lynxi in Fig. 13.

FIG. 11.

Photograph of a section of trackway I1 of Canipeda longigriffa.

ECOLOGY AND BEHAVIOR The abundance of carnivores, both in number of trackways (15) and of species (60% of the recorded mammal species), is remarkable. Given the brief time span between ichnite production and burial, it is clear that much carnivore activity was concentrated in a small area (about 60 m2 ) during a short time. Considering the territorial behavior and foraging habits of comparable modern carnivores (Ewer, 1973; Kitchener, 1991; Wemmer, 1977), and their relative scarcity in modern ecosystems, it seems likely that something was exerting attraction on these animals, perhaps the presence of a carcass in the vicinity.

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FIG. 13. Reconstruction of trackmaker of trackway R1, Felipeda lynxi, based on the track measurements and on the anatomy of the fossil felid Pseudaelurus, with data from Ginsburg (1961a), and Turner and Ant´on (1997).

The need of drinking water would likely have attracted herbivores and carnivores in a more statistical proportion (Cohen et al., 1991). The presence of four parallel felid trackways that cross the site in a Northwest direction (Fig. 2) is the first known example of group traveling in fossil felids. There are several trackways of other carnivores and ungulates, crossing randomly with these parallel trails, and implying that there was no natural obstacle, such as the lake shore, forcing the animals to travel in the same direction. The most conservative interpretation would be that three adult-sized cubs were walking alongside their mother. This would indicate that, as in modern cats, cubs remained with their mother at least until reaching nearly adult size (Kitchener, 1991). ACKNOWLEDGEMENTS We thank Jes´us Alonso and Carmelo Corral from the Museo de Ciencias Naturales de Alava for their support and help during the excavation works. Financial support on fieldwork was provided by Museo de Ciencias Naturales de Alava. We are grateful to Spencer Lucas and Joanna Wright for their useful comments on the manuscript. Lourdes Casanovas told two of the authors (G.L. and R.S.) about the chance finding of the site by Petra Laumen.

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