Figure 1.
Phylogenetic relationships of sea turtles (Chelonioidea).
The alternative positions of Chelonioidea within Cryptodira according to (A) Joyce [40] and (B) Shaffer [41]. Alternative relationships of chelonioid species following the hypotheses of (C) Gaffney and Meylan [202] (Natator depressus was not included in that analysis) and (D) Thomson and Shaffer [43]. For further details see Werneburg [44]. Names of higher taxa follow Gaffney and Meylan [202]. Silhouette images not to scale.
Figure 2.
The skulls of two sea turtles.
(A, C, E, G, I, and J) Caretta caretta (XT757/07) and (B, D, F, H, K, and L) Lepidochelys kempii (M009/08). The cranium in (A and B) lateral, (C and D) palatal, and (E and F) dorsal views. The lower jaws and hyoid skeleton in (G and H) in dorsal view. The left lower jaw in (I and K) lateral and (J and L) medial view. add. fos, adductor fossa, add.cha, adductor chamber, ANG, angular; ART, articular; ARY, arytaen; BO, basioccipital; BS, basisphenoid or sphenoid; cav.tym, cavum tympanicum; CB1, cornu branchial-I; CB2, cornu branchial-II; CHL, cornu hyale; COH, corpus hyoidei; COR, coronoid bone; cr.sup, crista surpaoccipitale; DEN, dentary; dep, depression; EX, exoccipital; Fon, fontanelle; FR, frontal; JUG, jugal; MX, maxilla; OP, opisthotic; orb, orbit; PAR, parietal; pit, pits; PMX, premaxilla; PORB, postorbital; post.dors.em, posterodorsal emargination; PRA, prearticular; PRFR, prefrontal; PT, pterygoid; PAL, palatine; add.cha, adductor chamber; nar, narial opening; QJ, quadratojugal; QU, quadrate; se, suture seam; she, shelf; SQ, squamosal; ST, stapes (columella); sul.mec, sulcus Meckeli; SUP, supraoccipital; SUR, surangular; sym, symphysis; tub, tubercle; vent.lat.em, ventrolateral emargination; VO, vomer. Scale bars = 10 mm.
Table 1.
Skeletal material examined. Skull length is measured along the midline from the tips of the premaxillae to a point level with the back of the quadrates. Units in mm.
Table 2.
Specimens dissected or CT scanned. Measurements taken correspond to those listed in Wyneken [8] as far as possible.
Figure 3.
Micro-CT slices of the sea turtle Lepiodochelys kempii (M009/08) showing muscle structures.
(A) coronal slice 520 of 980 and (B) parasagittal slice 193 of 675. apo.cno, coronar aponeurosis; CB1, cornu branchial-I; CB2, cornu branchial-II; MX, maxilla; mus, muscular structures; PAR, parietal; PORB, postorbital; PT, pterygoid; QJ, quadratojugal; QU, quadrate; SUR, surangular. Scale bars = 10 mm.
Figure 4.
The jaw joints of two sea turtles.
(A–D) Caretta caretta and (E–F) Lepidochelys kempii. The left quadrate condyle of specimen XT161/08 in (A) ventromedial view. Stereopairs of the (B) left quadrate condyle and (C) left articular of specimen XT161/08; (D) right articular surface of specimen XT144/08; and the (E) left quadrate condyle, and (F) left articular of specimen XT043/08. art.cond, articular condyle; QU, quadrate. Scale bar = 10 mm.
Figure 5.
The first four neck vertebrae of the sea turtle Lepidochelys kempii segmented from the micro-CT scan of specimen M009/08.
ant, anterior; AT, atlas; AX, axis; ce, centrum; cond, condyle; cot, cotyle; dors, dorsal view; ivn, intervertebral nodule; keel, keel; lat, lateral view; nu.arc, neural arch; nu.ca, neural canal; nu.sp, neural spine; post, posterior view; pozyg, postzygapophysis; prezyg, prezygapophysis; t.pr, transverse provess; V3, third vertebra; V4, fourth vertebra; ven, ventral view. Scale bar = 10 mm.
Table 3.
Muscular unit used in this paper (see also [44], [143], [152]).
Figure 6.
The ligamentum quadratomaxillare and coronar aponeurosis in two sea turtles.
The quadratomaxillar ligament in (A) Caretta caretta (XT161/08) in lateral view, (B) ventrolateral view to show its connection to the lower temporal fascia, and (C) after being cut and peeled back to show its medial surface. (D) the ligamentum quadratomaxillare in Lepidochelys kempii (XT043/08). (E) a stereo pair of the coronar aponeurosis in Caretta caretta (XT161/08). 19, the m. adductor mandibulae externus Pars profundus; 21a, m. adductor mandibulae externus Pars superficialis medial head; 21b, m. adductor mandibulae externus Pars superficialis posterior head; 21c, m. adductor mandibulae externus Pars superficialis lateral head; 45a, m. depressor mandibulae lateral part; 75, m. atlantoepistropheooccipitis; apo.cno, coronar aponeurosis (external tendon); cav.sul, cavum sulcus; cav.tym, cavum tympani; fascia, fascia; JUG, jugal; lig.qu.mx, ligamentum quadratomaxillare; palp.sca, palpebral scales; PORB, postorbital; QJ, quadratojugal; QU, quadrate; rha.low, lower rhamphotheca; rha.upp, upper rhamphotheca; SQ, squamosal; ST, stapes (columella); tro.oti, processus trochlearis otici; ven.lat.ema, ventrolateral emargination. Scale bars: (A) 50 mm; (C and G) 10 mm.
Figure 7.
The superficial adductor musculature in two sea turtles.
(A and B) Caretta caretta (XT161/08) and (C to G) Lepidochelys kempii (XT043/08). (A) lateral view of the head following removal of the skull roof and lateral skull wall. The adductor chamber in (B) anterolateral view, (C) dorsolateral view, (D) posterolateral view, (E) dorsolateral view with external adductors folded forwards to show the processus trochlearis otici, (F) posterodorsal view, (G) anterior view. 17, m. adductor mandibulae externus Pars medialis; 19, m. adductor mandibulae externus Pars profundus; 21a, m. adductor mandibulae externus Pars superficialis medial head; 21b, m. adductor mandibulae externus Pars superficialis posterior head; 21c, m. adductor mandibulae externus Pars superficialis lateral head; 23, the Pars pseudotemporalis principalis; 29, m. adductor mandibulae posterior Pars principalis; 45a, m. depressor mandibulae lateral part; 45b, m. depresor mandibulae, medial part; 75, m. atlantoepistropheooccipitis; apo.cno, coronar aponeurosis (“external tendón”); cav.tym, cavum.tym; clu, columella; lig.qu.mx, ligamentum quadratomaxillare; palp.sca, palpebral scales; n.V2, Ramus maxillaris n. trigemini; n.V3, Ramus mandibularis n. trigemini; OP, opisthotic; PAR, parietal; PORB, postorbital; rha.upp, upper rhamphotheca; rha.low, lower rhamphotheca; SQ, squamosal; tro.oti, processus trochlearis otici. Scale bars: (A) 50 mm; (G) 10 mm.
Figure 8.
Jaw muscle arrangement in the sea turtle Lepidochelys kempii (M009/08) based on reconstructions from micro-CT data.
Shown with (A) parts of the right side of the skull absent, (B) part of the m. adductor mandibulae externus Pars superficialis (No 21c) absent, (C) all of the m. adductor mandibulae externus Pars superficialis (No 21abc) and m. depressor mandibulae (No. 45) absent, (D) all of the m. adductor mandibulae externus and m. depressor mandibulae (No. 45) absent, (E) only the m. adductor mandibulae internus Partes pterygoidei (No. 26, 28) and (F) all muscle absent. 17, m. adductor mandibulae externus Pars medialis; 19, m. adductor mandibulae externus Pars profundus; 21a, m. adductor mandibulae externus Pars superficialis, medial head; 21b, m. adductor mandibulae externus Pars superficialis, posterior head; 21c, m. adductor mandibulae externus Pars superficialis, lateral head; 23, m. adductor mandibulae internus Pars pseudotemporalis; 26, m. adductor mandibulae internus Pars pterygoideus dorsalis; 29, m. adductor mandibulae posterior Pars principalis; 45, m. depressor mandibulae; apo.cno, coronar aponeurosis (“external tendón”); FR, frontal; MX, maxilla; OP, opisthotic; PAR, parietal; PRFR, prefrontal; PRO, prootic; PT, pterygoid; QJ, quadratojugal; QU, quadrate; SQ, squamosal; ST, stapes; SUP, supraoccipital; SUR, surangular; tro.oti, processus trochlearis otici. Scale bar = 10 mm.
Figure 9.
The origin and insertions of jaw muscles in two sea turtles illustrated using computer models based on micro-CT data.
(A–D and F) L. kempii (M009/08) and (E and G) C. caretta (XT757/07). (A) dorsolateral and (B) lateral view of the cranium with the temporal region removed. (C) medial view of the temporal region of the left cranium. (D) and (E): lateral views of the left lower jaw. (F) and (G) medial views of the left lower jaw. 17, m. adductor mandibulae externus Pars medialis; 19, m. adductor mandibulae externus Pars profundus; 21a, m. adductor mandibulae externus Pars superficialis medial head; 21b, m. adductor mandibulae externus Pars superficialis posterior head; 21c, m. adductor mandibulae externus Pars superficialis lateral head; 23, m. adductor mandibulae internus Pars pseudotemporalis principalis; 24, the Pars pseudotemporalis superficialis; 26, m. adductor mandibulae internus Pars pterygoideus dorsalis; 28a, m. adductor mandibulae internus Pars pterygoideus large medial head; 28b, m. adductor mandibulae internus Pars pterygoideus small lateral head; 29, m. ductor mandibulae posterior Pars principalis; 45a, m. depressor mandibulae lateral part; 45b, m. depressormandibulae medial part; 46, m. dilator tubae; 47a, m. branchiomandibularis visceralis small posterior head; 47b, m. branchiomandibularis visceralis large medial head; 75, m. atlantoepistropheooccipitis. Scale bars = 10 mm.
Figure 10.
The internal adductor musculature of two sea turtles.
(A–D) Caretta caretta (XT161/08), and (E–G) Lepidochelys kempii (XT043/08). (A) ventrolateral view of the left side adductor mandibulae internus, (B) ventral view of the right side internal adductors, (C) close up of the right side m. adductor mandibulae internus Pars pterygoideus ventralis, (D) posterior view of the internal adductors and hypaxial muscles, (E) ventral view of the right side of the palate, (F) medial view of the right lower jaw, (G) medial view of the right lower jaw after further dissection of the m. adductor mandibulae internus Pars pterygoideus. 19, m. adductor mandibulae externus Pars profundus; 21, m. adductor mandibulae externus Pars superficialis lateral head; 25, m. intramandibularis; 26, m. adductor mandibulae internus Pars pterygoideus dorsalis; 28a, m. adductor mandibulae internus Pars pterygoideus large medial head; 28b, m. adductor mandibulae internus Pars pterygoideus small lateral head; 45a, m. depressor mandibulae lateral part; 45b, m. depressormandibulae medial part; 46, m. dilator tubae; 86, m. longus colli Partes capitis-I et Pars capitis-II; 87, m. longus colli Partes capitis-I et Pars capitis-III; 88, m. retrahens capiti collique Pars carapaco-basiooccipitalis. ANG, angular; apo.cno, coronar aponeurosis; DEN, dentary; low.jaw, lower jaw; PRA, prearticular; QU, quadrate; rha.low, lower rhamphotheca; rha.upp, upper rhamphotheca; raphe, raphe; eus.tub, eustachian tube; zwi, Zwischensehne. Scale bars = 10 mm.
Figure 11.
Throat, tongue, and neck muscles of two sea turtles.
(B, C, F–H, J, and K) Caretta caretta and (A, D, E, I) Lepidochelys kempii. The throat muscles of specimen XT043/08 in (A) lateral view of the left side of (B) lateral view of the right side. The tongue of (C) specimen XT144/08 in dorsolateral view and of (D, E) specimen XT043/08 in dorsolateral view. The neck muscles of (F) specimen XT161/08 in dorsal view of the left side, (G) dorsolateral view of the right side, and (H) ventral view showing the m. longus colli (No. 86–87). (I) dorsolateral view of the right side of specimen XT043/08. Neck muscles of specimen XT161/08 in (J) lateral view of the left side, and (K) dorsolateral view of the left side. 19, m. adductor mandibulae externus Pars profundus; 21b, m. adductor mandibulae externus Pars superficialis posterior head; 42, intermandibular portion of m. constrictor colli; 45a, m. depressor mandibulae lateral part; 45b, m. depressormandibulae medial part; 46, m. dilator tubae; 47, m. branchiomandibularis visceralis; 52, m. plastro capitis; 53, m. squamosobranchiale; 55, m. branchiohyoideus; 57, m. collosquamosus; 58, m. coracohyoideus main part; 60, m. coracohyoideus small portion; 75, m. atlantoepistropheooccipitis; 80, m. collooccipitalis; 81+82, m. testocapitis et testooccipitis; 83, m. transversalis servicus; 86, m. longus colli Partes capitis-I et Pars capitis-II; 87, m. longus colli Partes capitis-I et Pars capitis-III; 88, m. retrahens capiti collique Pars carapacobasiooccipitalis; AT, atlas (approximate position); AX, axis; cav.tym, cavum tympanicum; CB1, cornu branchial-I; CB2, cornu branchial-II; COH, corpus hyoidei; lar, laryngeal entrance; PAR, parietal; PR, prootic; OP, opisthotic; SQ, squamosal; ST, stapes (columella); SUP, supraoccipital; tro.oti, processus trochlearis otici; cav.tym, cavum typanicum; V3, third vertebra; V4, fourth vertebra; V5, fifth vertebra. Scale bars: (A–D and F) 10 mm; (G and J) 50 mm.
Figure 12.
Neck muscle origins and insertions of two sea turtles illustrated using computer models based on micro-CT data.
(A and B) Caretta caretta (XT757/07) and (C, D, E and F) Lepidochelys kempii (M009/08). Posterior views of the cranium showing (A) the osteology and (B and C) sites of muscle insertion. Lateral views of the neck (D) with skull, (E) showing sites of origin for muscles 75, 80, 86 amd 87, and (F) showing the structure of muscles 75, 80, 86 and 87. 19, m. adductor mandibulae externus Pars profundus; 21b, m. adductor mandibulae externus Pars superficialis posterior head; 28b, m. adductor mandibulae internus Pars pterygoideus small lateral head; 45a, m. depressor mandibulae lateral part; 45b, m. depressormandibulae medial part; 46, m. dilator tubae; 53, m. squamosobranchiale; 57, m. collosquamosus; 75, m. atlantoepistropheooccipitis; 77, m. atlantooccipitis; 80, m. collooccipitalis; 81, m. testocapitis; 82, m. testooccipitis; 86, m. longus colli Partes capitis-I et Pars capitis-II; 87, m. longus colli Partes capitis-I et Pars capitis-III; 88, m. retrahens capiti collique Pars carapacobasiooccipitalis; AT, atlas; AX, axis; BO, basioccipital; EX, exoccpital; OP, opisthotic; PAR, parietal; PR, prootic; QJ, quadratojugal; QU, quadrate; SQ, squamosal; ST, stapes; SUP, supraoccipital; ten, tendon; V3, third vertebra; V4, fourth vertebra; V5, fifth vertebra. Scale bars = 10 mm.
Table 4.
Muscle features common to Chelonioidea. Compiled from Lakjer [76], Gnanamuthu [138]; Poglayen-Neuwall [136], [141], Schumacher [126], [141], [142], [149]–[151], Werneburg [44], [143], [152].
Figure 13.
Turtle skulls plotted against the topology of Shaffer (2009) with the addition of Proganochelys and Toxochelys.
Major phylogenetic groupings include (A) Testudinata, (B) Testudines, (C) Pleurodira, (D) Cryptodira, and (E) Chelonioidea. Euchelonioidae is used in the sense of Gaffney and Meylan [202]. Individual skulls represent (1) Lissemys punctata, (2) Chitra indica, (3) Carrettochelys insculpta, (4) Dermochelys coracea, (5) Chelonia mydas, (6) Lepidochelys kempii, (7) Eretmochelys imbricata, (8) Caretta caretta, (9) Chelydra serpentia, (10) Macrochelys temmincki, (11) Kinosternon subrubrum, (12) Sternotherus odoratus, (13) Stigmochelys ( = Testudo) pardalis, (14) Kinixys belliana, (15) Gopherus polyphemus, (16) Cuora amboinensis, (17) Melanochelys ( = Nicoria) trijuga, (18) Heosemys ( = Geoemyda) spinosa, (19) Clemmys caspica, (20) Terrapene ornata, (21) Graptemys geographica, (22) Malaclemys terrapin littoralis, (23) Emys blandingii, (24) Platysternon megacephalum, (25) Emydura sp., (26) Chelodina expansa, (27) Pseudemydura umbrina, (28) Chelodina novaeguinae, (29) Pelusios sinuatus, (30) Pelusios niger, (31) Podocnemis expansa, (32) Peltocphalus dumeriliana, and (33) Pseudemys floridana. Skulls re-drawn from Zangerl [30], Gaffney [29], [31], [177], and Matzke [22]. Taxonomy follows Fritz and Havaš [24]. Grey areas indicate orbits, braincase or naris whereas dark red indicates skull portions within an emargination. Note that the closest skull to the group name does not necessarily indicate the plesiomorphic condition for that group.