Halichoerus grypus (Fabricius, 1791)

Halichoerus grypus View in CoL (ZMUC 1485, NMW 28539)

From the lateral view, the snout of Paratethyphoca libera becomes narrower rostrally. Te rostral edge of the premaxilla is concave. In contrast, the nasal is almost parallel to the tooth row, and the rostral edge of the premaxilla is straight in Ha. grypus . Te nasal bone is narrower in Paratethyphoca libera (the medial width is 10% and the maximal width is 16% of the bone total length), while in Ha. grypus , they are equal to 15% and 24%, respectively

( Fig. S7 View Fig ). Te chin prominence is well-developed in Paratethyphoca libera and slightly developed in Ha. grypus . Te maximal height of the supraspinous fossa is smaller than the height of the glenoid fossa in Paratethyphoca ; contrary to Ha. grypus , the height of the supraspinous fossa is larger than the height of the glenoid fossa. Two ridges on the lateral side do not join near the glenoid in Paratethyphoca (vs. being joined in Ha. grypus ; Fig. S9 View Fig ). Paratethyphoca libera has the lesser tubercle of the humerus below the level of the head, and the proximal bifurcation of the deltoid crest is absent, while in Ha. grypus the lesser tubercle is higher than the head, and the proximal bifurcation in the deltoid crest is present ( Fig. S8 View Fig ). Te radius of Paratethyphoca libera is narrower in lateral view (28% of the bone length in Paratethyphoca , and 35% in Ha. grypus ).

Pusa hispida (ZMUC 803). Te rostral length of Paratethyphoca libera (from the nasal cavity to the orbit) is 25% of the occipital-nasal cavity length of the skull, while in Pu. hispida it makes 20%. Paratethyphoca libera has a larger minimal width of the interorbital bridge: 6% of the skull nasal cavity-occipital base length in Paratethyphoca ; and 3% in Pu. hispida . Te chin prominence is well-developed in Paratethyphoca libera and weakly developed in Pu. hispida . Paratethyphoca libera has a supraspinous fossa whose maximal height is shallower than the height of the glenoid fossa (vs. higher in Pu. hispida ). Two lateral ridges do not join near the glenoid in Paratethyphoca libera , and they are joined in Pu. hispida . Te humeral lesser tubercle is below the level of the head in Paratethyphoca libera and higher in Pu. hispida . Te proximal bifurcation of the deltoid crest is absent in Paratethyphoca libera and present in Pu. hispida . Te lateral epicondyle is weakly developed caudally in Paratethyphoca libera , and strongly developed in Pu. hispida . Te radius of Paratethyphoca libera is thinner from the lateral view—its maximum width is 28% of the bone’s total length, while it equals 32% in Pu. hispida .

Pusa caspica (NMW 66292–66299, GNM 2–2013/988). Te nasal cavity-orbital length of the rostrum is longer in Paratethyphoca libera , making up 25% of the nasal cavity-base of occipital length in Paratethyphoca libera and 20% in Pu. caspica ( Fig. S7 View Fig ). Te mandible of Paratethyphoca libera has a well-developed chin prominence, and its ventral edge is strongly concave, while Pu. caspica has a moderately developed chin prominence, and the ventral edge of the mandible is slightly concave. Te scapula of Paratethyphoca libera has a low supraspinous fossa (its maximum height is smaller than the height of the glenoid fossa), and lateral ridges are not joint near the glenoid, whereas in Pu. caspica , the maximum height of the supraspinous fossa is larger than the height of the glenoid fossa and the lateral ridges join together near the glenoid ( Fig. S9 View Fig ). Te humerus of Paratethyphoca libera has a lesser tubercle below the level of the head. Te proximal bifurcation of the deltoid crest is absent, and the lateral epicondyle is weakly developed in the caudal direction. In contrast, Pu. caspica has a lesser tubercle higher than the head, a well-developed proximal bifurcation of the deltoid crest, which in some individuals even joins with the lesser tubercle and the lateral epicondyle is well developed in a caudal direction ( Fig. S8 View Fig ). Paratethyphoca libera has a thin radius in lateral view; it makes only 28% of the bone length vs. 35% in Pu. caspica .

Phylogeny

Te parsimony tree with implied weighting places Paratethyphoca libera in the stem Phocinae , crownwards to most other fossil Phocidae except Pachyphoca ukrainica , Monachopsis pontica , Kawas benegasorum , and Nanophoca vitulinoides ( Fig. 12a View Fig ). In the total evidence analysis, for most statistics, Effective Sample Size is more than 200. Te exceptions (Effective Sample Size more than 100 for the second run) were in the: Diversification rate fossilised birth–death and turn over fossilised birth–death in both runs and prior, tree height, tree length, uncorrelated lognormal relaxed clock mean for morphological partition, and the rate for morphological partition. Paratethyphoca libera formed the clade with modern Phocinae and some Paratethyan taxa ( Pp. ukrainica and M. pontica ) ( Fig. 12b View Fig ). Based on the analysis, Paratethyphoca libera diversified from other Phocinae between 14.57 and 17.46 Ma (95% highest probability density: Table S10). In both trees, it is placed crownwards to Praepusa tarchankutica .

Generalized procrustes analysis

Two analyses were made for both humerus and femur. Te first analysis included all available Phocinae , with Paratethyan taxa (“ Pachyphoca ” sp., Praepusa sp. , Cryptophoca maeotica , Pontophoca sarmatica , Monachopsis pontica ). Also, another round of analyses excluded Phocini from the dataset: Phocini have a well-developed proximal bifurcation of the deltoid crest of the humerus—in contrast to other Phocinae (including Paratethyan taxa, which are in the focus of this article), which do not have such a strongly developed bifurcation; therefore, Phocini were found as outliers in the pooled dataset.

In the Generalized Procrustes Analysis of the humerus with Phocini, the PC1 described 25.9% of variation, the PC2—12%; without Phocini the PC1 described 19.1% of variation, the PC2—16.4%. In the Generalized Procrustes Analysis of the femur with Phocini, the PC1 described 24.4% of variation, the PC2—19.5%; without Phocini, the PC1 described 23.2% of variation, and the PC2—19.7%.

In the analysis of humeri with Phocini, the latter mostly occupied the negative side of PC1, while the other Phocinae (except Erignathus barbatus ) were on the positive side of PC1. Praepusa vindobonensis NWM SK 175, Cryptophoca maeotica , Monachopsis pontica were on the top right quarter of the plot, while Devinophoca emryi , “ Pachyphoca ” sp., Paratethyphoca libera MCFFM V-150, female Cystophora cristata and Pagophilus groenlandicus formed a cluster on the right - middle side of the plot. Pontophoca sarmatica NMNHU-P 1713-10 was situated between these groups ( Fig. 13a View Fig ). On PC1, the morphological variation is mostly observed in the shape of the distal extension of the deltoid crest and development of its proximal bifurcation. In negative coordinates of PC1, the distal extension of the deltoid crest is sharp, its proximal bifurcation is well developed, and the medial epicondyle is at the same level as the lateral one. In contrast, in positive coordinates, the distal extension of the deltoid crest is smooth, its proximal bifurcation is absent, and the medial epicondyle is lifted proximally compared to the lateral one. On PC2, the morphological variation is mostly seen in the length of the deltoid crest. In negative coordinates, the crest is short (about half of the bone), whereas in positive coordinates it is long (up to 70% of the bone length), and the humerus is mediolaterally compressed. In both PC1 and PC 2 in negative coordinates, the lesser tubercle is large, and it is higher than the proximal edge of the head, whereas in positive coordinates, it is small and situated lower than the head ( Fig. S11 View Fig ).

In the analysis of humeri without Phocini, Erignathus barbatus , Cryptophoca maeotica (except NMNHU-P 64–530), Praepusa vindobonensis NWM SK 175, and Devinophoca emryi form a group on the negative half of the PC1. Paratethyphoca libera MCFFM V-150, “ Pp.” chapskii and female C. cristata pooled together near the centre. M. pontica and Cr. maeotica NMNHUP 64–530 occupied the positive half of the PC2. “ Pp.” ukrainica was near the 0 value of the PC2, and on the positive half of the PC1, while Po. sarmatica NMNHUP 1713 -10 was between M. pontica and “ Pp.” ukrainica ( Fig. 13b View Fig ). On PC1, the morphological variation is mostly observed in the general humerus shape and position of the medial epicondyle. In negative coordinates of PC1, the humerus is gracile: the diaphysis and epiphysis are narrow, the humeral head is small, and the medial epicondyle is located slightly distally than the lateral one. In positive coordinates, the bone is more robust: the humeral head is large, and the diaphysis and epiphysis are wide; the medial epicondyle is located proximally to the lateral one. On PC2, the morphological variation is mostly seen in the length of the deltoid crest: in negative coordinates, it is as short as half of the bone, and in positive coordinates, it is longer than half of the bone, reaching the medial epicondyle. Also, in negative coordinates, the humeral head is proximally directed, and in positive coordinates it is more distally projected ( Fig. S11 View Fig ).

In the analysis of femur with Phocini, datapoints of the modern species formed a group with no distinguishable groups inside. Pontophoca sarmatica was separated from the other Phocinae . Monachopsis pontica made a compact group near the 0 value of the PC2 and a slightly positive half of the PC1. Another large cluster was located in the negative half of the PC1, near the 0 value of the PC2 and included Praepusa vindobonensis , Cryptophoca maeotica and “ Pachyphoca ” spp. ( Fig. 14a View Fig ). On PC1, the morphological variation is mostly observed in the sizes of the greater trochanter and medial epicondyle, and in the shape of the lateral edge of the diaphysis. In negative coordinates of PC1, the femur has a large greater trochanter, a short medial epicondyle and a strongly concave lateral edge of the diaphysis. In positive coordinates, the greater trochanter is small, the medial epicondyle is long (reaching the proximal half of the bone), and the lateral edge of the diaphysis is slightly concave. On PC2, the femur varies in general shape: the negative coordinates represent an elongated femur with a narrow distal epiphysis, the greater trochanter and the femoral head are small, and the condyles are similar in size. In positive coordinates, the femur is short and wide with a mediolaterally wide distal epiphysis, a robust greater trochanter, and the lateral condyle is larger than the medial one ( Fig. S12 View Fig ).

In the analysis of femur without Phocini, Pontophoca sarmatica was located separately from other Phocinae in the negative part of the PC2, and “ Pachyphoca ” spp. and Cryptophoca maeotica were on the positive half of the PC1 and negative half of the PC2. Monachopsis pontica was situated separately from Praepusa vindobonensis , Erignathus barbatus , and Cystophora cristata at the positive end of the PC1 ( Fig. 14b View Fig ). In negative coordinates of PC1, the femur is wide with a well-developed medial epicondyle, the femoral neck is long, and the greater trochanter is at the same level as the head. In the positive coordinates, the femur is narrow, its medial epicondyle smoothly connects to the bone diaphysis, the femoral neck is short, and the greater trochanter is higher than the head. On PC2, the femur varies in proportions of the greater trochanter and medial epicondyle and the shape of the lateral edge of the diaphysis. In the negative coordinates of PC2, the femur has a small greater trochanter, a large medial epicondyle (as long as the half of the bone), and the lateral edge of the diaphysis is slightly concave, whereas in positive coordinates the greater trochanter is large, the medial epicondyle is short, and the distal edge of the diaphysis is strongly concave ( Fig. S12 View Fig ).