Ratio between septal angle versus septal number for four mature specimens and one juvenile (CPC-1231).

<p>Specific correlative septal “events” are marked by dashed lines. D = diameter at the last septum.</p

Early ontogenetic internal shell development and measurements of <i>Salinites grossicostatum</i> based on four median sections.

<p>(a) CPC-1217, with sketch to the right (a₂) to illustrate internal shell structures; (b) CPC-1214; measurements are provided in mm.</p

Measurements of the siphuncle in five specimens.

<p>The upper plot illustrates the ratio between siphuncular diameter [DS] versus shell diameter [D]; the lower plot figures the siphuncular diameter versus apertural height at the plane of coiling [ah]. To the right, high-resolution scans illustrate the siphuncle; (a) longitudinal median section of CPC-1228; (b) transversal section through the plane of coiling in CPC-1214. Black arrows indicate position of the siphuncle; scale bars = 2.5 mm.</p

Ontogenetic reconstruction of <i>Salinites grossicostatum</i> based on external and internal characteristics.

<p>Sexual dimorphism and four major stages are recognized: embryonic, neanic, juvenile and mature. The diameter indicates the first occurrence of characteristic modifications.</p

Map of Mexico with inset of northeastern Mexico and the Jurassic-Cretaceous transition at Puerto Piñones.

<p><i>Salinites grossicostatum</i> specimens described here originate from a shaly limestone of the latest Tithonian “<i>Kossmatia-Durangites-Salinites</i> Beds” (cf. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0145865#pone.0145865.ref012" target="_blank">12</a>]), respectively the uppermost <i>Crassicollaria</i> Zone [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0145865#pone.0145865.ref008" target="_blank">8</a>]. Locality map after [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0145865#pone.0145865.ref013" target="_blank">13</a>]. Puerto Piñones: N25°02.719’/W101°03.396’.</p

Plot of shell diameter [mm] versus septum number for five specimens.

<p>Sexual dimorphism is indicated between septum numbers 25 and 30 by a considerably higher growth increase in macroconchs.</p

Size-frequency histogram for <i>Salinites grossicostatum</i>.

<p>Specimens were collected from a single layer of the uppermost Tithonian La Caja Formation at Puerto Piñones. D = diameter.</p

Apertural height (ah) versus shell diameter (D) for two micro- and two macroconchs (CPC-1214–1217).

<p>Note that apertural height is illustrated logarithmically. The regression lines indicate a change in growth at the primary constriction and that allometric growth is higher during post-embryonic stages than before.</p

The original Chan Hol II skeleton.

<p>Chan Hol II site prior to (<i>a</i>, <i>b</i>_<i>1</i>.<i>c</i>_<i>1</i>) and after (<i>b</i>_<i>2</i>, <i>c</i>_<i>2</i>) looting. About 10% of the skeleton remained on site, including the pelvis covered by stalagmite CH-7 (red arrows in Figs <i>b</i>_<i>1</i> and <i>b</i>_<i>2</i>).</p

Geographical position and site of the Chan Hol skeleton.

<p><i>a</i>: Location of submerged caves containing human skeletal remains dating to >8000 BP in the Tulum area of Quintana Roo, Mexico. Orange dots refer to human remains [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0183345#pone.0183345.ref020" target="_blank">20</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0183345#pone.0183345.ref021" target="_blank">21</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0183345#pone.0183345.ref025" target="_blank">25</a>]. The red dot marks Chan Hol II. <i>b</i>: The Chan Hol II archaeological site prior to looting. The arrow points to the CH-7 stalagmite analyzed here. (<i>c</i>) Reconstruction of the skeleton based on photographs of the site prior to looting. Note that the skeleton was originally complete and almost articulated (Photo courtesy Nick Poole and Thomas Spamberg).</p