Cryptophilus propinquus

Cryptophilus propinquus

Cryptophilus propinquus is a small (1.8-2.5mm) beetle in the family Pleasing Fungus Beetles (Erotylidae).
Cryptophilus propinquus - ID-ing details For details see with this image:
https://www.jungledragon.com/image/100284/cryptophilus_propinquus_-_lateral.html Cryptophilus,Cryptophilus integer,Cryptophilus propinquus,Erotylidae,Languriidae,compound eyes

Appearance

Beetles in the genus Cryptophilus are often confused with Cryptophagidae and are found on the same mouldy substrates, but differ in various structural elements, such as the shape of the antennae and the pronotum (as well as some ventral characters of legs/hips).
Cryptophilus propinquus - Lateral A little over 2mm. Often confused with Cryptophagidae, sometimes classified as family Languriidae or even in its own family Cryptophildae, nowadays mostly listed as part of the Erotylidae.
Used to be identified as Cryptophilus integer, but this species was split by Esser (2016). He studied the type of integer and concluded that this was conspecific with Micrambe abietis (Cryptophagidae), so he (eventually) split the old "integer" in two species: Cryptophilus angustus and C. propinquus.
My ID of this one as C. propinquus is based mostly on the shape of the pronotum, which is not a 100% clear character due to individual variability, but this one seems to be clearly enough in the propinquus-range imho.
Same beetle more dorsally:
https://www.jungledragon.com/image/100285/cryptophilus_propinquus_-_dorsal.html
Some close-ups of ID-ing details:
https://www.jungledragon.com/image/100286/cryptophilus_propinquus_-_id-ing_details.html Cryptophilus,Cryptophilus integer,Cryptophilus propinquus,Erotylidae,Geotagged,Germany,Languriidae

Naming

For the longest time this species would have been identified as Cryptophilus integer, but Esser (2016) found that this species was harbouring two separate distinguishable species. When studying the type of C. integer to see which of the two species should continue to carry the name integer, he found that the type of C. integer was in fact not a Cryptophilus, but conspecific with Micrambe abietis (Cryptophagidae), so the name integer had to be dropped for these altogether.
He split the two species previously known under the name "Cryptophilus integer" sensu auctorum into Cryptophilus propinquus and C. simplex, only to find out a year later (Esser, 2017) that the beetle previously known as Typhaea angusta was in fact a Cryptophilus and conspecific with C. simplex resulting in this species needing to be renamed to Cryptophilus angustus.
So the two species once known as Cryptophilus integer are now C. propinquus and C. angustus.

References:

Some text fragments are auto parsed from Wikipedia.

Esser, J. (2016) Über die Identität von Cryptophilus integer (Heer, 1841) (Coleoptera: Erotylidae). – Entomologische Nachrichten und Berichte 60(3/4), pp.213-218. (PDF)
https://www.researchgate.net/profile/Jens_Esser2/publication/313023199

Esser, J. (2017) On the Nearctic Cryptophilus Reitter, 1874 (Coleoptera: Erotylidae). – Linzer biologische Beiträge 49(2), pp.1133-1137. (PDF)
https://www.zobodat.at/pdf/LBB_0049_2_1133-1137.pdf

Esser, J. (2017) Was ist Typhaea angusta Rosenhauer 1856 (Coleoptera)? - Entomologische Nachrichten und Berichte, vol. 61(3/4), pp.177-179.
Taxonomy
KingdomAnimalia
DivisionArthropoda
ClassInsecta
OrderColeoptera
FamilyErotylidae
GenusCryptophilus
SpeciesCryptophilus propinquus
Photographed in
Germany