Due to being encased in
amber,
Cretoperipatus specimens preserve minute details that would otherwise be lost in the typical
fossilization process. One specimen (BU-001468) is preserved in three dimensions, allowing researchers to create an intricate
3D render of its anatomy. The undersides of the antennae possessed an array of
spindle-shaped sensilla. These papillae are similar to type 1 sensilla, but have a large, spindly-shaped basal piece. In addition to papillae, the animal possessed a pair of
frontal organs at the base of the antennae and beneath the eyes.
Mouth, jaws, and slime papillae Cretoperipatus had a
ventral (bottom-facing) mouth with two
internal jaws. In the original description, the animal's
genital pad was mistaken for the mouth.'''''' This was due to the
holotype (AMNH Bu218)'s poor preservation and the two structures looking superficially similar. In the specimens BU-001467 and ZZZ0066, the mouth wasn't preserved. However, the mouth of BU-001468 was partially exposed and preserved six oral lips (bean-like structures that surround the mouth). This indicates
Cretoperipatus had at least six oral lips on either side of its mouth. Since the jaws of BU-001467 were separated in the amber matrix, their structure is clearly discernible.
Cretoperipatus had an inner jaw blade with a large principal tooth (which resembles a large
claw). Lower down, the inner jaw blade had three smaller claw-like structures known as accessory teeth. Beneath these was a saw-like structure known as the denticle blade. This had 11
serrations called denticles. Rather than being connected, the denticle and inner jaw blade were separated by a piece of
tissue known as the diastemal membrane. This tissue tapered off near the serrated portion of the jaw and created a small gap called a diastema. Like other velvet worms,
Cretoperipatus possessed a pair of
slime papillae on the sides of its head. In BU-001468, these were preserved retracted. As a result, they were somewhat hard to distinguish, even when using
x-ray microscopy.
Trunk Cretoperipatus had around twelve plicae (bands) of
dermal papillae on each
segment of its trunk. Out of the twelve, seven plicae passed between the
legs and formed large continuous rings. Meanwhile, the other five were restricted to the animal's
dorsal (back) region and varied in length. The dorsal plicae had a pattern of one or two
accessory papillae separated by two
primary ones. On the other hand, the
ventral (underbelly) plicae lacked a set pattern and had smaller papillae overall. Certain regions of the trunk possessed crater-shaped papillae. These are a variant of accessory papillae with a central depression and a collar of scales. They come in two types differentiated by their shape and location. In
Cretoperipatus, the type 1 crater-shaped papillae were small, rounded, and had a collar made up of eight scales. These were randomly distributed on plicae near the legs. The type 2 variants were larger, elongated, and found in the interplical space (folds between the plicae). They were arranged in curved rows of six papillae, with two occurring between each set of legs. The first row was located on the animal's sides and curved upward, while the second row was on the underbelly and curved inward. When combined, the two rows formed a
convex lens. In addition to plicae and dermal papillae,
Cretoperipatus had a dorsomedial furrow (a long grove) running along the middle of its back. On its underside, the trunk preserved traces of the
preventral and ventral organs. These were rounded in shape and located on the midline of its body between each pair of legs. At the very end of the trunk,
Cretoperipatus had a
genital pad between its penultimate (second to last) pair of legs.
Lobopods Cretoperipatus had a pair of legs known as
lobopods on each
segment of its trunk. Based on complete specimens (BU-001467 and ZZZ0066), the animal had 22 pairs of legs. Like in other velvet worms, the lobopods had a
papillae-covered base,
spinose pads or cushions, and a clawed foot. The animal lacked
coxal organs on any of legs and lacked
crural papillae on the front-most pairs.
Cretoperipatus was originally described as having only three spiny pads per lobopod, However, better specimens show almost all of its lobopods have four. Oliveira et al. suggested that the original describers mistook the
holotype's back-most legs with its front, as this specimen was poorly preserved and a velvet worm's endmost legs have fewer cushions. On a typical leg of
Cretoperipatus, the
distal (furthest away from the trunk) and
proximal (closest to the trunk) cushions are thinner than the two in between. Leg pairs 1 and 2 have four spinous pads. Pair 3 was similar, but it also possessed a
vestigial fifth pad. This fifth pad was fragmented and split into four patches. Leg pairs 4 and 5 had only four pads. However, the third pad (the 2nd closest to the body) was split in two by a nephridial tubercle, an organ used to dispel
waste. Leg pairs 6 to 20 had the same structure as the 3rd: five spinous pads with a vestigial and fragmented fifth. The second to last (penultimate) pair of legs lacked a fifth pad. Instead, it had only four pads with the fourth being fragmented. Finally, matching what was observed in the holotype, the last (ultimate) pair of legs had only three spinous pads.
Feet and claws The
Cretoperipatus holotype had a foot with five basal papillae (
primary papillae found at the base of the feet), with the bottom-most two being weakly developed. None of the new specimens preserved basal foot papillae on any of their feet. At the end of the foot were two distal papillae (primary papillae found at the end of the feet). These were located on either side of a pair of claws. In the specimen BU-001467, many of its claws were detached and found floating in the
amber matrix. This indicates that, as in modern velvet worms, the claws are connected by only a fragile
membrane of
tissue. == Classification ==