Biological Conservation Assessment

Evolution

Taxonomy

KINGDOM:
Animalia

PHYLUM:
Chordata

CLASS:
Mammalia

ORDER:
Pholidota

FAMILY:
Manidae

GENUS:
Manis

SPECIES:
Manis pentadactyla

Evolutionary Pathways

Image Credit: Gaubert, 2018

Although pangolin morphology shares some similarity with South American anteaters and armadillos, they are phylogenetically distinct. Pangolins diverged from their closest relatives, the Carnivora, over 57 million years ago (MYA). There are 3 recognized genera, including the Manis (Asian pangolins), Smutsia (large African pangolins) and Phataginus (small African pangolins), which diversified from each other approximately 10 - 13 MYA. Within Asian pangolins, M. pentadactyla forms a clade (monophyletic group) with M. crassicaudata and M. javanica.

Evolutionary Relatives

Pangolins are commonly mistaken to be related to xenarthra (a clade of placental mammals that include anteaters and armadillos). They share similar features - including dental structure (a lack of teeth), abdominal muscles, a modified skull, and a fused tailbone region. However, new genetic research shows a closer relationship between pholidota and carnivorans (the most recent common ancestor of cats, dogs, and other flesh-eating mammals)! This may mean the similarities noticed with xenarthra occurred as the result of convergent evolution.

Image Credit: Naish, 2015

Evolutionary Genetics

Recent scientific studies have made an effort to study the genetic makeup of the Chinese Pangolin. In comparing the genetic variation of the different pangolin species, scientists discovered that the number of gene families unique to each pangolin species is 3 - 4 times greater than the number of gene families shared between the species.

New research has given insight into the genetics behind the scaled armor of the pangolin- comparative genetic analysis suggest that the scales (like those of an armadillo) may have developed as an analogous structure, playing a key role in immune system development. The image (right) shows how the interferon gene (critical for developing immunity) is significantly less present in pangolins than in other species. Scientists hypothesize that the the genes responsible for a pangolin's scales evolved as an added protection for their continued survival; this development most likely occurred 19 MYA, before the split of the African and Asian pangolins.

Taxonomic Traits

Family Traits

Animals in the family Manidae have scales made of keratin covering their body and share smooth, round skulls. They lack teeth, instead using their stomach to chew and digest food. They also share long tongues used to dig out insect food sources. Most tend to be nocturnal, though they can be active during the day as well.

Genus Traits

Animal in the genus Manis have the ability to roll their scaled bodies into a ball for protection. They have strong forelimbs and sharp claws used to forage food. Most of the synapomorphies (similarities shared because of a common ancestor) are related to the size and shape of their skeletal structure.

Species Traits

Chinese pangolins have 18 rows of hair-covered, overlapping scales. They have a small pointed head and a helmeted appearance, a narrow mouth, and round body with tapering tail. Their shorter claws and tails help distinguish them from other pangolins. They are a nocturnal species that is a predominantly terrestrial species (living on the ground). They can also emit a chemical smell when threatened (similar to a skunk).

References:

Born Free USA. (2021, September 9). Pangolins - facts, habitat, endangered status: Species spotlight. Retrieved from https://www.bornfreeusa.org/species/pangolins/

Choo, S. W., Rayko, M., Tan, T. K., Hari, R., Komissarov, A., Wee, W. Y., Yurchenko, A. A., Kliver, S., Tamazian, G., Antunes, A., Wilson, R. K., Warren, W. C., Koepfli, K. P., Minx, P., Krasheninnikova, K., Kotze, A., Dalton, D. L., Vermaak, E., Paterson, I. C., Dobrynin, P., Wong, G. J. (2016). Pangolin genomes and the evolution of mammalian scales and immunity. Genome research, 26(10), 1312–1322. https://doi.org/10.1101/gr.203521.115

Escobedo, M. (2022). "Manis". Animal Diversity Web. Retrieved from https://animaldiversity.org/accounts/Manis/

Gaubert, P., Antunes, A., Meng, H., Miao, L., Peigné, S., Justy, F., Njiokou, F., Dufour, S., Danquah, E., Alahakoon, J., Verheyen, E., Stanley, W. T., O’Brien, S. J., Johnson, W. E., & Luo, S.-J. (2017). The complete phylogeny of pangolins: Scaling up resources for the molecular tracing of the most trafficked mammals on Earth. Journal of Heredity, 109(4), 347–359. https://doi.org/10.1093/jhered/esx097

ITIS. (n.d.). Manis pentadactyla. Integrated Taxonomic Information System - Report. Retrieved from https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=584931#null

Naish, D. (2015, July 21). Surprises from placental mammal phylogeny 1: Pangolins are close kin of carnivorans. Scientific American Blog Network. Retrieved from https://blogs.scientificamerican.com/tetrapod-zoology/surprises-from-placental-mammal-phylogeny-1-pangolins-are-close-kin-of-carnivorans/

Naish, D. (2015, July 14). The refined, fine-tuned placental mammal family tree. Scientific American Blog Network. Retrieved from https://blogs.scientificamerican.com/tetrapod-zoology/refined-fine-tuned-placental-mammal-family-tree/

Raynor, S. (2022). "Manis pentadactyla". Animal Diversity Web. Retrieved from https://animaldiversity.org/accounts/Manis_pentadactyla/

Walters, S. (2022). "Manidae". Animal Diversity Web. Retrieved from https://animaldiversity.org/accounts/Manidae/

Keywords: phylogeny; clade; convergent evolution; variation; analogous structure

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