Mesomyzon mengae

Overview

Mesomyzon mengae is a fossil lamprey from Early Cretaceous freshwater deposits. An elongated snout, round oral disc, gill region, and trunk muscle segments are described. It invites examination of an ancient fish through body traces rather than small bones.^[1]

Key facts

Seven gill pouches were reported. The gill region behind the head and muscle segments of the trunk have also been studied. Examining repeated structures one by one reveals the elongated fish’s organization in greater detail.^[1]

Time and place

It is known from freshwater layers linked to the Jehol Biota in present-day Inner Mongolia, China. A 2006 study introduced its occurrence as Early Cretaceous, about 125 million years ago. The material reveals a lamprey that lived in ancient fresh water.^[1]

The time range describes source context, not the complete duration of this species.

Size, form and skeleton

An elongated snout, well-developed disc-shaped mouth, and extended gill region are described. The trunk preserves repeated muscle segments. Its body can be examined by following several structures from head toward tail.^[1]

Four adult Mesomyzon mengae specimens studied in detail in 2021 had total lengths of about 15–21.7 cm. Their elongated bodies and round mouths survive together, vividly revealing an ancient lamprey form.^[4]

Habitat and reproduction

The disc-shaped mouth and gill structures are important features for recognizing a lamprey body. This species was studied from fossils in freshwater deposits. Comparing the mouth, respiratory region, and trunk muscles explores the organization of an aquatic vertebrate.^[1]

Fossil discovery

A 2006 study examined reference specimen IVPP V14719, complete specimen IVPP V14718A, and other material. When describing the type specimen’s dorsal fin and tail, the paper also referred to separate specimen V14718A. Several specimens of one species supplemented information about different body regions.^[1]

References

1. Chang et al. (2006) — A fossil lamprey from the Jehol Biota of China
2. Gess et al.2006 — A Devonian lamprey from South Africa
3. Chang, Zhang & Miao2006 A lamprey from the Cretaceous Jehol biota of China, Nature441:972–974
4. Wu et al. (2021) — New adult specimens of Mesomyzon

Research questions

How similar were ancient lamprey bodies to living forms? Oral discs, gill pouches, and repeated trunk muscles can be compared. Examining well-preserved regions in different specimens reveals the form of one species.^[1]

Observation

Move your gaze from the round oral disc through the gill region to the trunk muscle segments. Look for different repeated structures within the elongated outline.^[1]