Spanish in Equatorial Guinea is the only example of Spanish as a principal or national language in Sub-Saharan Africa. It is not the first language of people in the country, but it is a language used publically and formally throughout the country, sort of like how English is used in India. The development of this dialect is very different than most other dialects of Spanish, and it shares a lot of features with the Latin American dialects that were influenced by slaves brought in.
Equatorial Guinea is a small country (CIA World Factbook says slightly smaller than Maryland), consisting mainly of the island of Bioko and a mainland sandwiched between Cameroon and Gabon. The largest city is Malabo, with only about 50,000 people. The country in total has about 500,000 inhabitants.
The Portuguese discovered the island of Bioko in 1471, and soon the island became a sort of way-station for the slave trade. After a lot of bickering back and forth, Spain finally got control of the territory through the Treaty of el Prado in 1778, but they didn't really begin colonizing until 1858. The main colonizers wer emissionaries, freed slaves from Cuba, and Catalans from Catalonia in Northeastern Spain.
In 1964, Equatorial Guinea was granted autonomy, and in 1969 it gained its independence and was ruled by the dictator Francisco Macías Nguema, who destroyed the basic infrastructure and expelled many ethnic groups, for the next 11 years. the country is still recovering from his rule with the aid of outside countries, Spain among them.
The principal ethnic groups are the Fang and Bubi (many of whom were exterminated my Nguema). There are also the Bujeba, Combe, Benga and others. The indigenous languages of these groups for the most part belong to the Bantu family, one of the largest language groups in Africa.
Spanish is mainly used in communication between the various ethnic groups, and in national contexts. It was illegal to teach Spanish in the schools during the reign of Nguema, so there is a whole generation whose proficiency in Spanish is sub-par. Also, Spanish here has undergone a sort of creolization, as would be expected of a European language introduced into a region to where many actual Europeans do not move. Here is the general phonology and morpho-syntax of the dialect:
- there's a lot of vowel shifting: /i/>/e/, /e/>/i/, /e/>/a/, /a/>/e/, /o/>/u/, /u/>/o/. There's nothing regular about it except that something gets changed. Sometimes they'll even put a diphthong wher eit wouldn't normally be, or add a consonant in between two vowels.
- The voiced plosive stops /b/, /d/, /g/ often disappear between vowels, so that for instance lago will become something like /lao/
- Syllable-final /s/, while becoming /h/ or completely dropped in many dialects, is often pronounced, but can occur anywhere near the alveolar region, so it can range from /θ/ to /s/ to /š/.
- /x/ is also usually lost, or changed into /g/ or /γ/, so that caja can become /'kaa/, /'kaga/, or /'kaγa/.
- /n/ and /ñ/ are also often lost intervocalically (This also happened when Portuguese and Galician developed from Iberian Latin or Old Spanish), or /n/ will become /ñ/ before /i/ or /e/. In an intervocalic position, /ñ/ will become /j/ sometimes so cañon will become /ka'jon/.
- /rr/ is usually simplified to /r/ or becomes /dr/, so perro will be /'pero/ or /'pedro/
- /j/ is often lost before /e/ and /i/, and 'll', normally /j/ or /λ/, can become /l/, so that calle becomes /'kale/.
- Theres an interchangeability between /f/ and /θ/ that is very common.
- Voicless pulmonic stops /p/, /t/, /k/ can become voiced inbetween vowels.
I can't really take credit for all this work, all I did was translate a fellow student of mine's website: http://www.tulane.edu/~spanling/Guinea_Ecuatorial/PROLOGO.html, and his sources are book on the matter by Manuel Alvar and John Lipski, two very prominent Spanish language linguists.