Can dentals be palatalized?

Question

In my native language, Russian, coronal stops and approximants are normally dentals. However, when they are "iotated", in addition to palatalization, it also changes their place of articulation to alveolar:

• t̪ → tʲ
• d̪ → dʲ
• n̪ → nʲ
• l̪ → lʲ

These also tend to be somewhat velarized when they are not palatalized. Wikipedia has this to say on velarization in the context of dentals:

For many languages, such as Albanian, Irish and Russian, velarization is generally associated with more dental articulations of coronal consonants.

My understanding is that velarization and palatalization is sort of mutually exclusive, because e.g. a palatalized velar consonant is practically indistinguishable from the corresponding palatal.

OTOH when looking at this table, dentals are in the same column as apical retroflex. Again, my understanding is that retroflex consonants also cannot be palatalized.

Looking for palatalized dentals in PHOIBLE, I only found entries for d̪ʲ|dʲ, t̪ʲ|tʲ, and t̪ʲʰ|tʲʰ. I'm not entirely sure what this notation actually means, but it's interesting that there's no "pure" d̪ʲ or t̪ʲ to be seen.

So, are palatalized dentals impossible in principle? And if so, what is the anatomical reason for that?

Answer 1

It is hard to say. Phoible suggests some candidate languages. In some cases (t̪ʲ|tʲ) the description in the original source is not clear enough that they (the compilers) can decide whether the segment is indeed dental. They do suggest it more definitively for Bulgarian and Russian, but that is "given these (listed) sources". We can add Rusyn, Northern Mansi, Votic, Lezgian, Mishmi and Yuma as languages reputed to have [t̪ʲ].

I weakly think that there is no language with a contrast between [tʲ] and [t̪ʲ] (based on a bit of fallible time with the Phoible database). A contrast would be more definitive proof that such a thing exists. Otherwise, the question is a matter of expert phonetic judgment, i.e. is the final consonant in "brother" in Russian a palatalized alveolar or a palatalized dental? Those kinds of judgments are extremely difficult to make, and most linguists would say "I can't say", since there isn't a clear basis for saying (auditory phonetics is a regrettably moribund art). However, one might find concrete phonetic evidence supporting the "dental, not alveolar" phonetic claim in the referenced literature.

Nonexistence of a particular sound is not necessarily related to anatomy: it might well be because of perception – X and Y are so close together that the probability of perceiving that both X and Y exist and are distinct is miniscule. There is a general analytic prejudice against "dental" as a category (embodied in the vagueness of the letter t in IPA), which translates into the t̪ʲ|tʲ uncertainty in Phoible, and which may make unlikely registering a segment [t̪ʲ] when it could equally plausible be called [tʲ].

Answer 2

There is certainly no phonetic reason that dentals cannot be palatalised.

Phonologically it's trickier. Contrasts between dentals and alveolars are already unusual (even the contrast between /θ/ & /s/ is not simply one of place of articulation, as /s/ is a sibilant fricative, whilst /θ/ is not; likewise their voiced & affricate counterparts). For a language to have phonemic palatalised dentals it would need t have this distinction on top of phonemic palatalisation.

As @user726 says in their answer, from PHOIBLE it does not appear that any language contrasts /t̪ʲ/ & /tʲ/.

I would suggest this is not a result of an impossibility of the phonemic contrast, but simply due to the extreme rarity of a phonemic contrast between dental and alveolar stops.