Mammuthus meridionalis vestinus, Azzaroli, 1972

Konidaris, George E., Kostopoulos, Dimitris S. & Koufos, George D., 2020, Mammuthus meridionalis (Nesti, 1825) from Apollonia- 1 (Mygdonia Basin, Northern Greece) and its importance within the Early Pleistocene mammoth evolution in Europe, Geodiversitas 42 (6), pp. 69-91 : 72-74

Mammuthus meridionalis vestinus

(Azzaroli in Ambrosetti, Azzaroli,

Bonadonna & Follieri, 1972) ( Figs 2-4 )

HOLOTYPE. — Skeleton including the skull with the m3/M3 (Spanish Fortress, L’Aquila, Italy).

TYPE LOCALITY. — Madonna della Strada (Scoppito, L’Aquila, Italy).

LOCALITY. — Apollonia-1 (Mygdonia Basin, Macedonia, Greece).

AGE. — Late Villafranchian (Early Pleistocene).

MATERIAL EXAMINED. — Right maxilla fragment with DP2-DP3, APL-225; right M3 fragment, APL-686A; left M3 fragment, APL- 686B; right hemi-mandible with m3, APL-716; left m3, APL-687.

DESCRIPTION

The right maxilla fragment APL-225 preserves the DP2 and DP3 ( Fig. 2 ). The DP2 has rectangular shape and is formed of four, only slightly worn plates, with the posterior one attached to the third one. Cementodonty is present, but weak. The still not completely erupted DP3 consists of eight mostly unworn plates, which are parallelsided and separated. The tooth presents a weak lingual curvature. In lingual view, the first two plates are slightly inclined relative to the occlusal surface, whereas the rest are almost vertical.

APL-686B ( Fig. 3 A-C) is identified as upper molar based on the obtuse angle that is formed between the occlusal surface to the vertical plane of the lamellae, and on the rootward tilt for the last 6-7 lamellae ( Lister et al. 2013). It represents the third (last) molar due to the tapering form at the posterior end of the crown ( Lister et al. 2012). The plates were found loose and isolated in the sediment, and they were subsequently glued together. Preserved are thirteen plates, although at least one more should have been anteriorly, increasing thus the PN to possibly 14. The tooth is curved at the lingual side. In labial and lingual views, the plates are slightly inclined relative to the horizontal occlusal surface, and they are rather straight. The only complete enamel loop is the anterior-most preserved one. The enamel loops at the anterior part of the tooth are parallelsided, separated, perpendicular to the long axis of the tooth, and their lateral sides are rounded and evenly directed (not curving anteriorly or posteriorly). Apical digitations (appearing on the occlusal surface as rounded loops) are present at the third and fourth preserved lamellae. The fourth lamella, which is at an early wear stage, shows four subequal rings. The enamel folding is weak. The last eight plates are ovoid of wear.APL-686A corresponds to a fragmented upper molar and preserves only four plates. It was found close to APL-686B and represents possibly its right counterpart.

The hemi-mandible APL-716 preserving the m3 (see below) lacks the anterior part of the ventral border of the corpus, the condyle and the coronoid process ( Fig. 4 ). The mandibular symphysis is not well-preserved, but its preserved dorsal surface is straight and steeply directed downwards. In lateral and medial views, the hemi-mandible is relatively short and deep. The corpus is moderately swollen and more evident in the medial side. In lateral view, the depth of the corpus is higher at the level of the anterior part of the m3. The lateral side of the ramus is flat. Corpus and ramus form obtuse angle due to the posterior inclination of the ramus. The rostral margin of the ramus is positioned at a minor obtuse angle, but almost vertical, to the alveolar planum. Two anterior mental foramina (AMF) are located at the posterior border of the symphysis, at the level of the anterior end of the m3, and a large medial mental foramen (MMF) is present approximately at the same level as the AMF. Measurements [in mm; according to Beden (1983)], are A = (220); B = (120); C = 260; F = 150 and J = (225).

The molar on the hemi-mandible APL-716 ( Fig. 4 ) is considered as the third one due the long antero-posterior dimension (length) and the narrowing of the crown towards the posterior end. The anterior part is worn down to a dentine platform and the original plate number can only be estimated, due to the wear of the enamel loops. However, the rostral part of the anterior root is visible, indicating that no substantial loss should had happened due to wear, which resulted possibly in the loss of only the anterior talon ( Lister & Sher 2015). Therefore, the number of plates is estimated as 12, plus a platelet/talonid at the posterior end. The shape of the molar is elliptic, being wider in the middle, and with a minor curvature at the labial side. In lingual view, the plates are slightly inclined relative to the occlusal surface. In labial view, the tooth shows a slight depression at the middle. Cement deposition is strong on the occlusal surface, as well as on the labial, lingual and posterior sides; however, the enamel is high above the cement. The enamel loops (five complete at the anterior part) are parallel-sided and separated. Anteriorly, the loops are oblique relative to the long axis of the tooth and become perpendicular to that at the posterior end. Apical digitations are few and present posteriorly. The enamel folding is undulating and present at the entire length of the enamel figure. The lateral sides of the enamel figures are rounded and directed anteriorly, stronger on the lingual side.

The identification of the APL-687 ( Fig. 3 D-F) as a third lower molar is based on the significant preserved length despite the advanced dental wear (a condition possible only in the last molars when the forward progression of them has been terminated), and on the presence of a single root; the anterior first and second roots had been lost, and therefore a substantial part of the original anterior end of the tooth is missing ( Lister et al. 2012; Lister & Sher 2015). The tooth preserves seven visible plates, whereas at least one more should be added in the anterior part, where the dentine is confluent. Due to its strong wear, the original plate number, as well as the crown height, cannot be estimated. The lamellar frequency, measured at the base of the crown, results in a low value ( Table 1 ), because of the divergence of the plates towards the base in elephantids ( Lister & Sher 2015). The shape of the molar is almost parallel-sided. In labial and lingual views, the tooth shows a slight depression at the middle. Cement covers the regions between the enamel loops as well as the labial, lingual and posterior sides. At the anterior-medial part of the tooth, complete enamel loops are present, which are parallel-sided with anterior and posterior median swellings that are slightly offset from the long axis of the molar (asymmetry). The enamel loops are separated, albeit in some lamellae they are almost in contact, and are oblique relative to the long axis of the tooth. The lateral sides of the enamel figures are rounded. Apical digitations are present on the two distal plates; the last plate, which is at an early wear stage shows four subequal rings. The enamel folding is regular, more intense than APL-716, due to the advanced stage of wear ( Van Essen 2011); it is present at the entire length of the enamel figure.

Age at death

The ontogenetic age is estimated using the dental-wear-based age criteria for the extant African savannah elephant Loxodonta africana provided by Laws (1966). The m3 APL-716 ( Fig. 4 ) falls within Laws’ group XXV, which corresponds to the average age of 49 in African Equivalent Years (AEY). Recent revisions on Laws’ age assignments propose that this age group corresponds to an upper limit of 50 AEY with 70+ longevity for the African elephant ( Stansfield 2015; Haynes 2017). Mammuthus meridionalis had a significantly larger body size than extant African elephants, and due to the general positive scaling of longevity to body size across mammals, also probably had a longer total lifespan ( Eisenberg 1990; Maiorana 1990); therefore, a slightly older true age is expected for APL-716. When the formula of Blueweiss et al. (1978) (longevity in days proportional to body mass in grams 0.17) is applied, assuming a longevity of 70 years and a body mass of 6.0 tonnes for males of L. africana , and an average body mass of 11.0 tons for M. meridionalis ( Larramendi 2016) , a longevity of approximately 77.5 years can be hypothesized for the latter. Consequently, the estimated upper limit of the ontogenetic age for APL-716 is 47 × 77.5/70 = 52 years. Accordingly, the estimated upper limit of the ontogenetic age for the m3 APL- 687 (Laws’ group XXVII; Fig. 3 D-F) is 66-73 years, for the M3 APL-686B (Laws’ group XX; Fig. 3 A-C) is 37 years and for the maxilla APL-225 (Laws’ group II; Fig. 2 ) is c. 1 year.

Figures

FIG. 2. — Right maxilla fragment with DP2-DP3 (APL-225) of Mammuthus meridionalis vestinus (Azzaroli in Ambrosetti, Azzaroli, Bonadonna & Follieri, 1972) from Apollonia-1: ventral (A), medial (B), and lateral (C) views. Scale bar: 5 cm.

FIG. 3. — Dental remains of Mammuthus meridionalis vestinus (Azzaroli in Ambrosetti,Azzaroli,Bonadonna & Follieri,1972) from Apollonia-1:A-C, left M3 fragment (APL-686B) in occlusal (A), buccal (B), and lingual (C) views; D-F, left m3 (APL-687) in occlusal (D), lingual (E), and buccal (F) views. Scale bar: 5 cm.

FIG. 4. — Right hemi-mandible with m3 (APL-716) of Mammuthus meridionalis vestinus (Azzaroli in Ambrosetti,Azzaroli,Bonadonna & Follieri,1972) from Apollonia-1 in lateral (A), dorsal (B), and medial (C) views. Scale bar: 10 cm.